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Spectrophotometry of occult blood in feces.

This method for measuring fecal occult blood is based on the heme-catalyzed oxidation of tetramethylbenzidine by H2O2. An aliquot of heated stool homogenate is mixed with acetic acid to chemically separate heme from globin. The heme is extracted into ethyl acetate and reacted with the reagent and H2O2 to produce a green oxidation product. The reaction is followed kinetically for 30 to 60 s at 660 nm. A660 is linearly related to the amount of hemoglobin. The lower limit of detection is 1 to 2 mg of hemoglobin per gram (wet weight) of feces. Within-day precision (CV) of the analysis for hemoglobin added to stool specimens (4 to 30 mg/g) ranged from 2.3 to 7.6%, between-day CV from 2.1 to 8.1%. Analytical recovery of hemoglobin added to fecal specimens (4 to 30 mg/g) ranged from 86.7 to 106.2%. Of the substances known to interfere with conventional dye-oxidation tests for fecal occult blood, only myoglobin and ascorbic acid interfere with hemoglobin quantification by our procedure. The test is fast, inexpensive, and easy to perform, and involves equipment available in hospital laboratories.

Benzidines↗

The "HemoQuant" test: a specific and quantitative determination of heme (hemoglobin) in feces and other materials.

We describe a new, specific, quantitative method for fecal blood, based on conversion of nonfluorescing heme to fluorescing porphyrins, that obviates serious deficiencies inherent in currently used tests. A two-reagent system is used to determine the two hemoglobin-related fractions that are found in feces. The hot citric acid extract includes only the variable fraction of porphyrins that have been preformed from heme in the intestinal tract; this often is the major fraction. Total hemoglobin is indirectly determined by reaction with heated oxalic acid:FeSO4 reagent, which converts the remaining heme to porphyrin without loss of the preformed porphyrins. A three-step purification procedure eliminates interfering materials. Analytical recovery of added hemoglobin is linearly related to concentration over a several-thousand-fold range. The assay is equally applicable to whole blood or to sub-microgram amounts of hemoglobin in the 8-mg (wet weight) fecal sample tested. Quality control by liquid chromatographic and fluorometric analysis documents fluorescence specificity of the heme-derived porphyrins.

Chromatography, High Pressure Liquid↗

Estimating meconium (fetal feces) concentration in human amniotic fluid by nuclear magnetic resonance.

Measurements are reported of NMR relaxation times (T2) on hydrogen in water of isotonic NaCl solutions and of normal human amniotic fluid in which known concentrations of meconium (fetal feces) were dissolved. Magnetic fields for resonance of 23.5 X 10(3) and 0.6 oersteds were used. From the measured T2 values, reliable estimates of meconium concentrations could be obtained that might be considered estimates of fetal distress. Observed minor variation of T2 values was probably due to the mucopolysaccharides comprising 80% of the meconium weight. Advantages of this technique for possible clinical use in obstetrics include small volume of sample required (0.1 ml), lack of necessity for sample filtration or centrifugation, and shortness of time required for analysis (less than 30 min).

Amniotic Fluid↗

Acrylonitrile-14C metabolism in rats: effect of the route of administration on the elimination of thiocyanate and other radioactive metabolites in urine and feces.

In Wistar rats, the elimination of the sum of radioactive metabolites of acrylonitrile--14C was not markedly influenced by the rote of acrylonitrile administration. The elimination of thiocyanate, however, was significantly higher after oral (23% of the dose) than after intraperitoneal (4%), subcutaneous (4.6%), or intravenous (1.2%) administration. The elimination of the sum of radioactive metabolites was highest in the first 4 hours after acrylonitrile administration and rapidly decreased, whereas the excretion of thiocyanate reached maximum between hour 8 and 14 after oral or intraperitoneal administration. Less than 1% of radioactivity of the acrylonitrile--14C dose was eliminated in feces irrespective of the route of administration.

Acrylonitrile↗

A low-molecular-size LM2 allergen in mite, Dermatophagoides farinae, extracts containing feces which elicits conjunctival reactions in patients with bronchial asthma.

A low-molecular-size antigen, LM2, which possesses a significant activity to elicit histamine release, was isolated from an ultrafilterable (Mr-cutoff < 10k) fraction of a mite extract containing feces by consecutive chromatography on Ultrogel AcA 54 and Sephadex G-25. The isolated antigen was still heterogeneous glycoproteins, giving a smeary band around pI 3-5 on an Ampholine PAG plate, with molecular weights of 6-8k and 4k on SDS-PAGE and Sephadex G-50 gel filtration, respectively. Chemical treatments of the antigen suggested that the epitope responsible for the elicitation of histamine release resided in the protein moiety. The antigen had activities to provoke conjunctival congestion and histamine release in mite-allergic patients, but not immunogenicity by itself. The antigen competitively inhibited the reactions of HM1, HM2, and HM3 fractions to corresponding antisera, but did not cross-react with anti-Der f I or anti-Der f II sera.

Allergens↗