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At least 433 records · Page 24Linked to original sources
PubMed1997

Gastric mucosal hydrophobicity in duodenal ulceration: role of Helicobacter pylori infection density and mucus lipids.

BACKGROUND & AIMS: Gastric mucosal hydrophobicity is reduced in Helicobacter pylori infection. Infection density is increased in duodenal ulcer (DU) compared with H. pylori gastritis alone, but it is unknown whether there is a corresponding difference in hydrophobicity or whether hydrophobicity is related to infection density or to mucus lipids. The aim of this study was to determine the relationship between H. pylori infection density and mucosal hydrophobicity, and between mucus lipids and hydrophobicity, and to compare results in patients with H. pylori-induced gastritis with and without DU. METHODS: Fifty-four patients, including 29 H. pylori-positive (15 with DU and 14 with gastritis alone) and 25 H. pylori-negative controls, were studied. Hydrophobicity was determined by goniometry and infection density by histology. Mucus lipids were determined by colorimetry and phospholipase A2 activity by radioenzymatic assay. RESULTS: Hydrophobicity was reduced in DU compared with gastritis alone (39 degrees vs. 48 degrees; P < 0.05) and with healthy controls (39 degrees vs. 60 degrees; P < 0.0001). Hydrophobicity correlated with infection density (Rs = -0.55; P < 0.01). Mucus triglyceride level was modestly increased with infection, but mucus phospholipids or lipolysis were unrelated to H. pylori and hydrophobicity. CONCLUSIONS: Mucosal hydrophobicity is reduced in H. pylori-positive patients with DU compared with those having gastritic only. Hydrophobicity correlates with infection density but not with mucus lipid levels.

Adult↗
PubMed1977

The suitability of the dry ashing procedure for determination of arsenic in marine samples.

The dry ashing procedure with Mg/(NO3)2/Mgo ashing aid, followed by arsenic determination by colorimetry, has been compared to an X-ray fluorescence method for determination of arsenic in marine samples. Good agreement between these techniques indicated the suitability of the dry ashing, colorimetric procedure for determination of "fish-arsenic". A wet digestion procedure using HNO3-H2SO4-HC104 was also shown to be suitable.

Animals↗
PubMed1981

Variability in the content and composition of alkaloids found in Canadian ergot. I. Rye.

The total alkaloid content and individual alkaloid composition were determined by colorimetry and high performance liquid chromatography, respectively, for Canadian rye ergot sclerotia. The total alkaloid content was highly variable between sclerotia from the same head, field, or region and ranged from 0.011 to 0.452% (av. 0.249%). Levels were lowest in ergot from Prince Edward Island. The individual alkaloid composition was uniform throughout a single sclerotium or in different sclerotia from the same head, somewhat uniform for averages in different fields throughout a region, but highly variable from head to head in a given field. On a regional basis, ergotamine followed by ergocristine were the major alkaloids observed in the east whereas the order was reversed in the west. Ergometrine, ergosine, ergocornine, and ergocryptine were also observed to a lesser degree; ergostine was not observed. Isomerization of ergometrine increased from near 0% in the east to about 40% in the west, but was relatively constant (about 30%) for the peptide alkaloids in all regions.

Canada↗
PubMed1979

Determination of vitamin D in foods: a review.

Determining vitamin D content in foods is difficult because in natural foods of highest vitamin D activity, and even in vitamin D-fortified foods, only small quantities are present, and many other compounds are extracted along with vitamin D that cause difficulties in purifying the extract or in the spectrophotometry or colorimetry that follows. Several physicochemical methods--such as spectrophotometric, colorimetric, thin-layer chromatographic, adsorption, partition, gas-liquid, and high-performance column chromatographic--have been tried for assay foods for vitamin D, but none of them have been accepted for official or routine use; they are time consuming and expensive, or lack the required sensitivity, precision, or accuracy. Curative biological assays, based on degree of healing of a leg bone of rats previously made rachitic, is the generally accepted method to determine vitamin D content of foods. However, that method also requires too much time and is expensive. The recently developed high-performance liquid chromatographic method may offer the most for establishing a satisfactory physicochemical method for determining vitamin D in foods. Many of the difficulties and problems in assaying foods for vitamin D are discussed.

Animals↗
PubMed1979

Field evaluation of selected monitoring methods for phosgene in air.

Four selected methods have been evaluated and field tested as candidates for a specific, continuous procedure for monitoring phosgene in air at or below concentrations of 0.05 ppm. The methods evaluated were automated colorimetry, gas chromatography, infrared spectrophotometry and a recently developed paper tape monitor. A standard manual colorimetric procedure was used as a reference method. The paper tape, infrared and automated gas chromatographic techniques most closely fulfilled the criteria set forth for an "ideal", selective, continuous procedure for phosgene.

Air Pollutants↗
PubMed1992

Performance of laboratories measuring silica in the Proficiency Analytical Testing program.

A statistical study was performed on the results reported by laboratories analyzing silica samples in the first 101 rounds of the Proficiency Analytical Testing (PAT) program. Five laboratories participated in the first round of the PAT program in 1972, and participation grew to 130 laboratories before falling to 105 in Round 101. The laboratories use all three of the major methods of analysis: colorimetry, x-ray diffractometry, and infrared spectroscopy. The objectives of the study were to determine bias between methods, the variability associated with the methods, and any changes in bias or variability caused by a number of factors. The colorimetric method has consistently given the lowest results, particularly at higher loadings. X-ray diffractometry results were biased higher than infrared spectroscopy results during one period but not in the following period. Between the two periods, the procedures and materials used to prepare PAT samples changed in a number of ways, but the switch to quartz dust with a smaller particle size is a likely explanation for the bias difference. Generally, silica analyses have improved in precision over time, and this improvement has taken place for all three of the methods. The colorimetric method has shown the poorest precision of the three methods, but, unlike the differences in bias, the differences in precision have diminished considerably over time. Precision estimates from other studies were compared to those from this study to learn more about sources of variability. The largest source of variability, the differences between laboratories, was large even when laboratories used the same method, as they did in a collaborative study of silica methods.

Air Pollutants, Occupational↗
PubMed2002

Instrumental measurements of skin color and skin ultraviolet light sensitivity and risk of cutaneous malignant melanoma: a case-control study in an Italian population.

The authors evaluated objective measurements of constitutive skin color and ultraviolet light sensitivity in relation to risk of cutaneous malignant melanoma (CMM). Incident CMM cases (n = 183) were diagnosed between December 1994 and January 1999 at the Maurizio Bufalini Hospital in Cesena, Italy. Controls (n = 179) were mostly spouses/partners of cases and were frequency-matched by age and sex. In addition to interviews, constitutive skin color and skin ultraviolet light sensitivity were assessed by colorimetry and minimal erythema dose (MED), respectively. Odds ratios were estimated using unconditional logistic regression. The odds of CMM increased by a factor of 1.20 (95 percent confidence interval: 1.12, 1.30) for each unit of skin brightness and by a factor of 1.24 (95 percent confidence interval: 1.07, 1.43) per 10 mJ/cm(2) of MED. These associations were largely independent of phenotypic or sun-related characteristics and were modified by sun exposure. Increased risk of CMM was observed only among subjects with the highest levels of sun exposure. Epidemiologic studies of CMM may benefit from the inclusion of colorimetric and MED measurements along with traditional risk factors to obtain more accurate, quantitative, and objective information.

Adolescent↗
PubMed1996

Correlation between colorimetric and protein-precipitation assays of tannins dissolved in treehole water.

There was a significant correlation between colorimetric and protein-precipitation assays of tannins dissolved in treehole water. The protein-precipitation potential of early-season treehole water was extremely low relative to total phenolics measured by colorimetry. The protein-precipitation method is recommended because it directly measures protein binding, the property of dissolved tannins relevant to mosquito development. Furthermore, the procedure is not affected by treehole water color and does not produce dangerous wastes.

Colorimetry↗
PubMed2001

Development of a sensitive multi-well colorimetric assay for active NFkappaB.

The transcription factor nuclear factor kappaB (NFkappaB) is a key factor in the immune response triggered by a wide variety of molecules such as inflammatory cytokines, or some bacterial and viral products. This transcription factor represents a new target for the development of anti-inflammatory molecules, but this type of research is currently hampered by the lack of a convenient and rapid screening assay for NFkappaB activation. Indeed, NFkappaB DNA-binding capacity is traditionally estimated by radioactive gel shift assay. Here we propose a new DNA-binding assay based on the use of multi-well plates coated with a cold oligonucleotide containing the consensus binding site for NFkappaB. The presence of the DNA-bound transcription factor is then detected by anti-NFkappaB antibodies and revealed by colorimetry. This assay is easy to use, non-radioactive, highly reproducible, specific for NFkappaB, more sensitive than regular radioactive gel shift and very convenient for high throughput screening.

Animals↗
PubMed2000

Cytotoxicity assessment of Ma-huang (Ephedra) under different conditions of preparation.

Ma-huang is a traditional Chinese medicinal herb derived from EPHEDRA: sinica Stapf and other EPHEDRA: species, used to treat asthma, nose and lung congestion, and fever with anhidrosis. It contains 0.5-2.5% by weight of total alkaloids, of which ephedrine accounts for 30 to 90%. Recently, large amounts of ma-huang were used as a source of ephedrine in many dietary supplements formulated for weight reduction, because ephedrine has been found effective in inducing weight loss in diet-restricted obese patients. However, indiscriminate consumption of ma-huang-containing products has resulted in many cases of poisoning, some of which were fatal. The objective of this study is to investigate the relative toxicity of ma-huang extracted under different conditions. The toxicities of various extracts were assayed using MTT colorimetry on a battery of cell lines, while ephedrine alkaloids were analyzed with HPLC. The results are summarized as follows. (1) The cytotoxicity of all ma-huang extracts could not be totally accounted for by their ephedrine contents, suggesting the presence of other toxins in the extracts. (2) Grinding was a significant condition enhancing the toxicity of the extracts. (3) The relatively high sensitivity of the Neuro-2a cell line to the toxicity of ma-huang extracts suggests that the toxic principles were acting on neuronal cells. (4) One condition to produce a ma-huang extract with high ephedrine-to-toxins ratio would be to boil the whole herb for two h.

Cell Survival↗
PubMedDate not supplied

Color technology in video endoscopy.

The psychophysical aspects of the color experience and the clinical significance of color during video endoscopy are introduced in this paper. This introduction includes a description of how colors are rendered in video endoscope systems along with basic colorimetry, the science of color. Together these provide the clinical engineer with an understanding of color and a method of effectively communicating color information. The ability to standardize color rendition in video endoscopy systems is not yet available. Nonetheless, an argument is presented in favor of the clinical engineer normalizing color rendition in video endoscope systems in the hospital and educating the clinicians on managing endoscopic system color performance in the clinical setting.

Biomedical Engineering↗
PubMed1993

Quantitating cataract and nuclear brunescence, the Harvard and LOCS systems.

Subjective and objective systems are used to quantify cataract at The Center for Clinical Cataract Research. We have described each system and its use, presented data on reproducibility and validity, and for objective systems, demonstrated the correlation to the subjective grade of the cataract as defined by the Lens Opacities Classification Systems, Versions II and III (LOCS II and III). The subjective systems are used to classify nuclear color, nuclear opalescence, cortical cataract, and posterior subcapsular cataract. Reported kappa scores for LOCS II range from 0.85 to 1.0. Intraclass correlation coefficients for LOCS III (r1) range from 0.67 to 0.94. The computerized objective system are: (1) fast spectral scanning colorimetry (FSSC) for assessment of nuclear color (r1 = 0.96 to 0.98); (2) nuclear mean density (NMD) for assessment of nuclear opalescence (r1 = 0.97); and (3) percent area opacity (anterior = a; posterior = p) (OPAC-a and OPAC-p) for assessment of cortical and posterior subcapsular cataract (r1 = 0.92 to 0.96).

Adult↗
PubMed1999

Accuracy of the plasma amino acid-consumption test in detecting pancreatic diseases is due to different methods.

The aim of this study was to evaluate the controversial specificity of the plasma amino acid (AA)-consumption test in detecting pancreatic diseases by using two different quantitative methods. A total of 55 subjects: 13 healthy subjects, 13 patients with chronic pancreatitis (three mild/moderate, eight severe), 13 patients with pancreatectomy and complete suppression of the exocrine pancreatic secretion, eight patients with chronic liver disease (five with impaired synthetic function), and eight patients with chronic renal failure. Total plasma AAs were quantified by a colorimetric method (p-benzoquinone) in all subjects, at 0, 30, 45, and 60 min during and 30 min after minute 60 of i.v. cerulein infusion (50 ng/kg/h). Either total and individual AAs were quantified by chromatography (high-performance liquid chromatography; HPLC) in 10 healthy subjects, 10 patients with pancreatectomy, and 10 with chronic pancreatitis at 0 and 60 min after the start of the cerulein infusion. For the colorimetric method, healthy subjects had maximal percentage decreases of total AA concentrations not significantly different from those of patients with pancreatectomy and significantly higher than those of patients with chronic pancreatitis (p < 0.0001) or chronic liver disease (p < 0.001). Pancreatic function, as assessed by fecal elastase-1 test, was not significantly correlated to the maximal percentage decrease in total plasma AAs. For the chromatographic method, total AA concentrations were not significantly correlated to those determined by colorimetry. The concentration of each of the individual plasma AAs varied considerably in each group. Fecal elastase-1 values were normal (> or = 200 microg/g) in all patients without pancreatic disease and in only one of 11 patients with chronic pancreatitis and exocrine insufficiency. The type of method used can explain the different results of the AA-consumption test. This test is not very specific for the pancreas.

Adult↗
PubMed1997

An imaging colorimeter for noncontact tissue color mapping.

There has been a considerable effort in several medical fields, for objective color analysis and characterization of biological tissues. Conventional colorimeters have proved inadequate for this purpose, since they do not provide spatial color information and because the measuring procedure randomly affects the color of the tissue. In this paper an imaging colorimeter is presented, where the nonimaging optical photodetector of colorimeters is replaced with the charge-coupled device (CCD) sensor of a color video camera, enabling the independent capturing of the color information for any spatial point within its field-of-view. Combining imaging and colorimetry methods, the acquired image is calibrated and corrected, under several ambient light conditions, providing noncontact reproducible color measurements and mapping, free of the errors and the limitations present in conventional colorimeters. This system was used for monitoring of blood supply changes of psoriatic plaques, that have undergone Psoralens and ultraviolet-A radiation (PUVA) therapy, where reproducible and reliable measurements were demonstrated. These features highlight the potential of the imaging colorimeters as clinical and research tools for the standardization of clinical diagnosis and for the objective evaluation of treatment effectiveness.

Algorithms↗
PubMed1991

Photoelectric quantitative evaluation of argon laser treatment of port wine stains.

Sixty patients with port wine stains were treated with the argon laser and graded visually into four subjective categories for changes in skin colour. For objective quantitative evaluation a photoelectric colorimeter was used. Reproducible definition of the lightness of the lesions into numbers was obtained. Differentials in lightness between normal contralateral skin and the port wine stain before and after treatment were quantified for each individual. The objective evaluation revealed a statistically significant difference between the four categories (P less than 0.05). The best clinical therapeutic effect was found to correlate with only 80-90% blanching. The average lightening obtained was 46.5%. Local heating of port wine stains in 12 patients showed no measurable darkening in the colour of the lesions, whereas the normal contralateral skin reacted with marked reddening. Determination of changes in lightness by photoelectric colorimetry provides an objective, quantitative means to evaluate the effects of laser treatment of port wine stains.

Adolescent↗
PubMed1993

Topical tretinoin (retinoic acid) improves melasma. A vehicle-controlled, clinical trial.

Melasma is a common disorder of cutaneous hyperpigmentation predominantly affecting the faces of women. Little is known about the aetiology of melasma, and treatment is frequently disappointing. Topical tretinoin is of benefit in treating other forms of hyperpigmentation, for example liver spots, and we therefore investigated its effectiveness in melasma. Thirty-eight women completed a randomized, vehicle-controlled study, in which they applied 0.1% tretinoin (n = 19) or vehicle cream (n = 19) once daily to the face for 40 weeks. At the end of treatment 13 (68%) of 19 tretinoin-treated patients were clinically rated as improved or much improved, compared with 1 (5%) of 19 in the vehicle group (P = 0.0006). Significant improvement first occurred after 24 weeks of tretinoin treatment. Colorimetry (an objective measure of skin colour) demonstrated a 0.9 unit lightening of tretinoin-treated melasma and a 0.3 unit darkening with vehicle (P = 0.01); these results correlated with clinical lightening (r = 0.55, P = 0.0005). Histologically, epidermal pigment was reduced 36% following tretinoin treatment, compared with a 50% increase with vehicle (P = 0.002). Reduction in epidermal pigment also correlated with clinical lightening (r = -0.41, P = 0.01). Moderate cutaneous side-effects of erythema and desquamation occurred in 88% of tretinoin-treated and 29% of vehicle-treated patients. Topical 0.1% tretinoin produces significant clinical improvement of melasma, mainly due to reduction in epidermal pigment, but improvement is slow.

Administration, Topical↗
PubMed1995

Transepidermal water vapour loss is not increased during and following dithranol irritation.

Dithranol is established as a very successful treatment for psoriasis. Its main disadvantages are irritation and staining at sites of application. The aim of the present study was to elucidate further the mechanism of dithranol-induced irritation, in particular to what extent this is related to an impairment of the skin barrier. Dithranol 3% in cream, paste and petrolatum was applied to the forearm skin of 20 volunteers and left in situ for 1 h. Transepidermal water loss (TEWL) was measured during a period of 2 weeks following dithranol application. In addition, a visual scoring system and colorimetry were used to assess erythema. The study showed conclusively that TEWL was not affected by the application of dithranol, even though pronounced erythema occurred.

Adult↗