PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Chromogenic Compounds”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 883 records · Page 49Linked to original sources
PubMed1999

Persistence of an [E1-, polymerase-] adenovirus vector despite transduction of a neoantigen into immune-competent mice.

The ability of a uniquely modified [E1-, polymerase-] adenovirus (Ad) vector to persist after the transduction of the bacterial beta-galactosidase gene into the livers of nontolerant, immune-competent adult mice was compared with an identical gene transfer attempt with an [E1-] Ad vector. After transduction, the E1-deleted vector was rapidly eliminated, but the modified vector persisted for at least 2 months (experiment duration). Modified vector persistence was also accompanied by prolonged transgene expression and decreased hepatotoxicity profiles. This result was in contrast to several reports suggesting that the transgene expressed by an Ad vector is the primary determinant of Ad vector elimination in vivo. Our results implied that the rapid immune clearance of Ad-transduced cells in vivo is codependent on the presence of two stimuli, or "hits." Hit 1 is due to Ad vector-derived gene expression while hit 2 is due to transgene immunogenicity. Attenuation of the first hit by the use of a significantly modified vector (such as the [E1-, polymerase-] Ad vector) allowed for extended persistence, despite the continued presence of the transgene-derived stimulus (hit 2). We discuss how the two-hit hypothesis is in fact congruent with a number of other reports that have analyzed Ad vector persistence in immune-competent animals. On the basis of our results, [E1-, polymerase-] Ad vectors should have broad benefits for use in human gene therapy situations in which the encoded transgene may be perceived as a neoantigen by the intact human immune system.

Adenoviridae↗
PubMed1985

Total phospholipid analysis in human milk without acid digestion.

A colorimetric method for measuring the organic phosphorus in human milk without acid digestion was studied. Human milk samples were assayed and compared to phosphatidylcholine, phosphatidylethanolamine, and sphingomyelin standards. Spectral and calibration curves prepared from phospholipid standards were equivalent. Absorption maxima occurred between 720 and 740 nm. A reproducibility study of twenty total lipid samples had a coefficient of variation of 3.8%. Phosphorus ranged from 4.7 to 5.5 micrograms with a mean +/- SD of 5.2 +/- 0.2 micrograms P. The recovery of phosphatidylcholines added to 10 mg samples of human milk triacylglycerols ranged from 99.0 to 102.1%. The results from the new method were comparable to those obtained by a modified Fiske and Subbarow method for measuring inorganic phosphorus after sulfuric acid digestion of the milk lipids. We concluded that the new method provides a satisfactory alternative for the determination of organic phosphorus in human milk.

Acids↗
PubMed1995

A simple chromogenic substrate assay of tissue factor pathway inhibitor activity in plasma and serum.

A simple chromogenic substrate assay for the quantitation of tissue factor pathway inhibitor (TFPI) activity in plasma or serum samples was developed. After immobilization on microtiter plates for 20 hours at 4 degrees C, a commercial thromboplastin was incubated for 1 hour at room temperature with 1 U/mL of a prothrombin complex concentrate (Protromplex). After washing, solid-phase Factor Xa activity was measured by a chromogenic substrate (S-2222). Factor Xa generation was progressively inhibited when increasing amounts (1-12 microL) of heated serum or plasma, and recombinant TFPI (1-5 ng/mL), were coincubated with Protromplex. Inhibition by serum or plasma was abolished by anti-TFPI polyclonal antibodies. Plasma levels of TFPI in 25 healthy volunteers were found to be 0.98 +/- 0.19 U/mL (range 0.71-1.52), with an intra- and inter-assay coefficient of variation of 10.7 and 11.1%, respectively. The use of a recombinant human thromboplastin improved the sensitivity and reproducibility of the assay. Plasma levels of TFPI were found to be normal in 10 women at the end of their pregnancies, in 10 patients receiving oral anticoagulant therapy, and in 10 diabetic patients. Significantly higher levels were detected in 10 patients with chronic liver disease and in 10 patients with unexplained juvenile thrombosis. In patients with cardiovascular disease, a 7-day treatment with subcutaneous standard heparin increased TFPI activity. The availability of a simple and rapid assay to measure TFPI that does not require purified coagulation proteins may facilitate studies of the pathophysiologic relevance of this inhibitor.

Adolescent↗
PubMed1981

Alternate chromogens as substitutes for benzidine for myeloperoxidase cytochemistry.

Myeloperoxidase staining methods for classification of leukemias have traditionally employed benzidine dihydrochloride as the chromogen. Recent Occupational Safety and Health Administration regulations have classified benzidine as a carcinogen, which severely restricts its use in the clinical laboratory. Twenty-two specimens from normal control subjects and leukemia patients, previously classified by FAB criteria, were stained with benzidine and two alternate chromogens, diaminobenzidine and Hanker-Yates reagent (p-phenylenediamine and pyrocatechol). In a random, blind fashion, three experienced observers scored the stains from each case according to quality of smear, degree of peroxidase positivity, tinctorial distinction between nucleus and cytoplasm, and overall acceptability of the stain. All three observers rated the substitute chromogens as adequate for routine myeloperoxidase cytochemical staining. It is concluded that either of the methods studied would have clinical utility and can substitute for benzidine as a myeloperoxidase chromogen.

Benzidines↗
PubMed1983

Antithrombin III and plasminogen: a comparison of two synthetic substrate-based methods.

We have evaluated and compared the DuPont aca and the KABI/CentrifiChem synthetic substrate-based methods for the quantitation of plasma plasminogen (PLG) and antithrombin III (AT III). Method precision was evaluated using normal human pooled plasma (NHP) as sample. Within-day and day-to-day PLG assays generated a CV of 2.0% and 2.9%, respectively, for the aca method. For the KABI/CentrifiChem PLG method, within-run (within-rotor) analysis produced a CV of 1.7%, and day-to-day analysis produced a CV of 5.3%. The relationship between the aca (y axis) and the KABI/CentrifiChem (x axis) methods for PLG was found to be y = 0.99X - 1.4%, r = 0.979. Within-day precision for AT III by the aca method generated a CV of 4.6%, and day-to-day analysis produced a CV of 7.0%. The KABI/CentrifiChem AT III method generated a CV of 4.2% and 4.4% for within-run and day-to-day assays, respectively. The AT III correlation demonstrated a relationship of y = 0.84X + 15.2%, r = 0.952. The AT III and PLG reference ranges as established in our laboratory for healthy adults, pregnant women, and for cord blood specimens also are presented.

Adult↗
PubMed1983

False assignment of familial antithrombin III deficiency with the von Kaulla assay.

As a serum assay, the von Kaulla assay for antithrombin III has been criticized on the grounds that consumption of antithrombin III during in vitro blood clotting may lead to falsely low assay values. Use of the assay to screen a Utah pedigree for familial antithrombin III deficiency lends support to this criticism. In all, the assay was performed on 150 persons. Low values on the assay were corroborated by performing an alternative coagulation assay, an amidolytic assay, and an immunoassay. While all persons with historic evidence for a diagnosis of familial antithrombin III deficiency had low assay values, eight of 23 persons with low values had normal values on the other assays.

Adolescent↗
PubMed1984

Comparative investigation of a quantitative chromogenic endotoxin assay and blood cultures.

In a prospective study, the clinical relevance of a quantitative chromogenic endotoxin assay in plasma (detection limit 10 ng/L, assay time 2.5 hours) versus blood cultures was evaluated in 51 critically ill patients with increased susceptibility for infectious complications. Of the 400 samples tested, the endotoxin assay and bacterial culture both were negative in 342 samples. In 21 samples from 15 patients, gram-negative aerobic microorganisms were cultured. Corresponding endotoxin assays were positive in 14 samples (mean 100 ng/L). Twenty-three samples grew gram-positive bacteria. The associated endotoxin assays all were negative. Twelve samples were found to be endotoxin-positive without a corresponding gram-negative bacterial culture. In 7 of these 12 positive endotoxin assays, a laboratory or clinical explanation for these positive tests could be provided. In view of the high sensitivity, specificity, and predictive values obtained, the authors conclude that the endotoxin assay used is a useful clinical adjunct for both the detection and exclusion of gram-negative septicemia.

Bacterial Infections↗
PubMed1985

Occult blood testing using tetramethylbenzidine in an extraction procedure for patients on unrestricted diets.

An extraction test for stool occult blood was developed using 3,3', 5,5' tetramethylbenzidine (TMB), which gave reliable results in the presence of interfering substances, such as vitamin C, meat fibers, and vegetable enzymes. The new test was applied to 1,320 fecal specimens from hospitalized patients not on dietary restrictions. Of 189 specimens unequivocally positive by slide tests, 48 were negative by the extraction test, 42 were trace reactions, and 99 were 2+ to 4+. Extraction testing was performed on 351 of the 1,082 specimens negative by slide tests. Four of these were from patients taking supplemental vitamin C. Two of these specimens were extraction test positive ( ) and two were extraction test negative. One other specimen, from a patient not on supplemental vitamin C, was extraction test positive. Forty-nine specimens gave equivocal results, with two commercial slide tests for occult blood. By the extraction test, 26 of these were negative, 13 had trace amounts of blood, and 10 were 2+ or 4+.

Ascorbic Acid↗
PubMed1985

Comparison of a chromogenic prothrombin time with clotting prothrombin time in the assessment of clinical coagulation deficiencies.

A chromogenic prothrombin time (CPT) has been compared with the standard prothrombin time (PT) or activated partial thromboplastin time (aPTT) in evaluating the hemostatic abnormality in patients with specific clotting factor deficiencies or liver disease and in patients receiving anticoagulant or fibrinolytic therapy. As expected, the CPT was sensitive to deficiencies of Factors II, V, X, and VII but was unaffected by deficiencies of Factors XII, XI, IX, or VIII. Due to the presence of polybrene in the thromboplastin formulation, the CPT was insensitive to heparin concentrations below 1 unit/mL. However, the assay result prolonged progressively between 1 and 10 units of heparin/mL, indicating that the CPT can be used to assay heparin concentrations within this range. Among patients with liver disease or who were receiving warfarin or fibrinolytic therapy, there was good correlation between the prolongation of the PT and the CPT. The results demonstrate that the CPT was sensitive to the commonly encountered clinical abnormalities in which the PT is prolonged and could be applied for monitoring oral anti-coagulant therapy. However, prolongation of the PT to a given value in different clinical conditions was associated with different degrees of prolongation of the CPT. This differential effect may reflect an abnormality in fibrinogen conversion to fibrin, which prolongs the PT but not the CPT and may also be contributed to by the differential sensitivity of the PT and CPT to specific factor deficiencies. The simplicity and reproducibility of the CPT warrant its further assessment, but correlation with the PT in a variety of clinical conditions is needed before clinical application can be undertaken.

Anticoagulants↗
PubMed1987

Fully automated antithrombin-III assays by synthetic substrate on the Multistat III.

Antithrombin-III assays are performed to assess response to heparin therapy and efficacy of antithrombin concentrate therapy and in diagnosing hereditary thrombophilia, deep venous thrombosis, pulmonary embolus, and disseminated intravascular coagulation. Synthetic substrate assays for antithrombin-III are the methods of choice; however, most existing assay systems are semiautomated. A fully automated, antithrombin-III assay using the Kabi Chromogenic Synthetic Substrate S-2238 COATEST on the MULTISTAT III has been developed. This assay was compared with the Dade Protopath fluorometric assay. The correlation (r-sq) between the two assay systems was 0.82. Additionally, a three-way assay comparison was also performed, incorporating a new fluorometric substrate for antithrombin-III. The three-way comparative assays revealed correlation as follows: MULTISTAT III fluorometric assay and the MULTISTAT III/Kabi COATEST assay r-sq = 0.90; MULTISTAT III fluorometric assay and the Dade fluorometric assay r-sq = 0.86; and the MULTISTAT III/Kabi COATEST assay and the Dade Protopath fluorometric assay r-sq = 0.95. These automated assays were extremely cost effective and were a fraction of the cost of performing other types of antithrombin-III assays.

Antithrombin III↗
PubMed1989

A double-blinded comparative evaluation of three media for chromophore testing with viridans and nutritionally variant (deficient) streptococci.

A double-blinded prospective comparison of chromophore testing among 109 clinical isolates of alpha-hemolytic gram-positive cocci and 48 strains of nutritionally variant (deficient) streptococci (NVS) for its sensitivity, specificity, and predictive value under stimulated clinical laboratory conditions was performed after growth in three different media--Todd-Hewitt broth supplemented with 10 micrograms/mL of pyridoxal (THBP), THBP with 0.8% (w/v) yeast-extract (THBP + YE), and a semisynthetic chemically defined medium with Todd-Hewitt dialyzate (CDMT). The chromophore detection rates of Streptococcus mitis were 60.7, 67.9, and 78.6% after growth in THBP, THBP + YE, and CDMT, respectively. After growth in THBP there was significantly lower chromophore detection than either THBP + YE or CDMT for NVS (P less than 0.001), with a trend toward significantly less detection for S. mitis (0.15 greater than P). For Streptococcus sanguis II the detection rates were 45.7, 57.1, and 54.3%, respectively, for each medium. There was no significant difference between the detection rates after growth in THBP + YE or CDMT. One NVS was persistently chromophore negative, the first so described. There was a similar number of presumably false positive chromophore S. sanguis I strains (3 of 12) detected after growth in THBP + YE or CDMT. The sensitivity of chromophore detection for NVS (pooling results in THBP + YE and CDMT) was 95.8% and specificity was 59.6%. For a nonvariant streptococcus, the sensitivity was 61.9% and specificity was 93.5% for an isolate to be either S. mitis or S. sanguis II.

Chromogenic Compounds↗
PubMed1989

Heightened sensitivity of quantitative ELISA for IgM rheumatoid factor with the use of the biotin-streptavidin system.

Rheumatoid factors (RFs) have been traditionally detected by the agglutination of IgG-coated particles such as latex beads or erythrocytes. These agglutination assays are only semiquantitative and do not detect materials other than pentameric IgM RF. In order to optimize a quantitative enzyme-linked immunoassay (ELISA) for IgM RF that could be used for detecting small amounts of IgM RF in materials derived from large numbers of biologic fluids, several steps were investigated. In comparison with an ELISA using a peroxidase-conjugated antibody, substitution of a biotinylated antibody followed by peroxidase-conjugated streptavidin led to a steeper slope of absorbance versus U/mL of RF without increasing the background. By using as a chromogenic substrate tetramethylbenzidine (TMB) instead of o-phenylenediamine (OPD), an even steeper slope and a lower background were achieved. The biotin-streptavidin ELISA proved to be more sensitive than a commercial latex agglutination test and similar in sensitivity to a screening slide-agglutination test using IgG-coated human erythrocytes. When sera that had had positive results in tube-dilution assays both with sensitized human erythrocytes and sensitized sheep erythrocytes were compared with other sera with positive results for only agglutination of sensitized human cells but not sheep, the group with positive results for both tube dilution assays had higher IgM RF levels by ELISA than those in the group with only the positive assay for sensitized human cells.

Bacterial Proteins↗
PubMed1999

Requirement for a different hydrophobic moiety and reliable chromogenic substrate for endo-type glycosylceramidases.

A series of synthetic lactosides with aglycones that differed in length and structure were used to determine the substrate specificity of endo-type glycosylceramidases. Endoglycoceramidases (EGCase) from bacteria preferred lactosides with an acylamide structure over simple n-alkyl lactosides. While ceramide glycanase (CGase) from leech did not show preference. N -Acylaminoethyl beta-lactosides and n -alkyl lactosides were substrates for both EGCase and CGase, but N-acylaminobutyl beta-lactosides, whose acylamide residue differs from that in ceramide, were not hydrolyzed by EGCases. Thus, EGCases, but not CGase, appear to require an N-acyl group at the same position as that of intact glycosphingolipid for substrate recognition. A p-nitrophenyl lactoside derivative possessing an N-acyl chain was degraded by both EGCases and CGase and this chromogenic substrate may be an alternative substrate for endo-type glycosylceramidase activity. Km of the chromogenic lactoside for CGase and Rhodococcus EGCase were 28 microM and 2.9 mM, respectively.

Chromogenic Compounds↗
PubMed2004

Six spectroscopic methods for detection of oxidants in urine: implication in differentiation of normal and adulterated urine.

Six separate methods to detect oxidants in urine were developed. The presence of the oxidants was established by initial oxidation of ferrous to ferric ion and detecting the ferric by chromogenic oxidation or complex formation. The reagents for chromogenic oxidation were N,N-dimethylamoino-1,4-phenylenediamine (DMPDA), 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid (ABTS), and 2-amino-p-cresol (APC), and the reagents for the chromogenic complex were xylenol orange (XO), 8-hydroxy-7-iodo-5-quinolinesulfonic acid (HIQSA), and 4,5-dihydroxy-1,3-benzene-di-sulfonic acid (HBSA). All methods showed comparable results when tested for ferric, chromate, permanganate, oxychloride, hydrogen peroxide, oxone, tert-butylhydroperoxide, and cumenehydroperoxide at a concentration of 1.0 mmol/L in water (CV < 7%). The nitrite results are comparable only with DMPDA and APC. Periodate responded to the highest oxidation number (ON = 8) by chromogenic oxidation but lowest (ON = 2) by the chromogenic complex. The iodate responded only to the chromogenic oxidation with ON = 6. The linearity of the procedures was established by chromate in water. The linear concentrations were 0.09-12.00 mE/L for DMPDA, ABTS, APC, and HBSA and 0.09-6.00 mE/L for XO and HIQSA. In all methods, the correlation coefficients were > or = 0.9991 and precisions were within +/- 5.6%. The methods were used to test oxidants in 238 urine specimens. The chromate at 3.0 mE/L in water was used as standard. The correlation coefficients of 0.9600-0.9853 and the ANOVA test (F = 0.90, F(critical) = 2.22 at P(0.48)) indicated that the methods correlated well. The median concentration of oxidants in the specimens was 0.21 mE/L with an average and standard deviation of 0.62 +/- 1.19 (range 0.04-8.83 mE/L). When Grubbs' statistical test was applied to the specimen results, no specimen was found to be outlier or could be considered as adulterated. The Grubbs' test also revealed that the threshold concentration to identify urine adulteration was 29 mE/L at confidence level of 99%.

Chromogenic Compounds↗
PubMed1996

Substrate specificities of pepstatin-insensitive carboxyl proteinases from gram-negative bacteria.

Pseudomonas carboxyl proteinase (PCP), isolated from Pseudomonas sp. 101, and Xanthomonas carboxyl proteinase (XCP), isolated from Xanthomonas sp. T-22, are the first and second examples of unique carboxyl proteinases [EC 3.4.23.33] which are insensitive to aspartic proteinase inhibitors, such as pepstatin, diazoacetyl-DL-norleucine methylester, and 1,2-epoxy-3(p-nitrophenoxy)propane. The substrate specificities of PCP and XCP were studied using a series of synthetic chromogenic peptide substrates with the general structure, P5-P4-P3-P2-Phe-Nph-P2'-P3' (P5, P4, P3, P2, P2', P3': a variety of amino acids, Nph is p-nitro-L-phenylalanine, and the Phe-Nph bond is cleaved). PCP and XCP were shown to hydrolyze a synthetic substrate, Lys-Pro-Ala-Leu-Phe-Nph-Arg-Leu, most effectively among 28 substrates. The kinetic parameters of this peptide for PCP were Km = 6.3 microM, Kcat = 51.4 s-1, and kcat/Km = 8.16 microM-1.s-1. The kinetic parameters for XCP were Km = 3.6 microM, kcat = 52.2 s-1, and kcat/Km = 14.5 microM-1.s-1. PCP showed a stricter substrate specificity than XCP. That is, the specificity constant (kcat/Km) of each substrate for PCP was in general < 0.5 microM-1.s-1, but was drastically improved by the replacement of Lys by Leu at the P2 position. On the other hand, XCP showed a less stringent substrate specificity, with most of the peptides exhibiting reasonable kcat/Km values (> 1.0 microM-1.s-1). Thus it was found that the substrate specificities of PCP and XCP differ considerably, in spite of the high similarity in their primary structures. In addition, tyrostatin was found to be a competitive inhibitor for XCP, with a Ki value of 2.1 nM, as well as for PCP (Ki = 2.6 nM).

Aspartic Acid Endopeptidases↗