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Biomedical subjects

M S Coleman

Publications and source records attributed to M S Coleman.

At least 37 records · Page 2Linked to original sources
PubMed1986

Isolation of mutant adenosine deaminase by coformycin affinity chromatography.

Adenosine deaminase is a purine salvage enzyme that catalyzes the deamination of adenosine and deoxyadenosine. Deficiency of the enzyme activity is associated with T-cell and B-cell dysfunction. Mutant adenosine deaminase has been isolated from heterozygous and homozygous deficient lymphoblast cell lines with the aid of an affinity matrix consisting of coformycin (a potent inhibitor of the enzyme) as the affinity ligand, bound to 3,3'-iminobispropylamine-derivatized Sepharose. Routinely, 80-90% of adenosine deaminase in crude cell homogenates could be bound to the material. Adenosine deaminase was specifically eluted by enzyme inhibitors or less efficiently by high substrate concentrations. Protein preparations isolated from several different deficient cell lines were highly purified and exhibited molecular weights identical to wild-type adenosine deaminase. This method produces a protein that is suitable for structural studies.

Adenine↗
PubMed1986

A method for biotinylating oligonucleotide probes for use in molecular hybridizations.

A new method is described for biotinylation of oligonucleotide probes for use in molecular hybridization reactions. Biotin-11-dUTP residues were added enzymatically, using terminal deoxynucleotidyl transferase, to the 3' terminus of a synthetic oligonucleotide prepared from the known nucleotide sequence for adenosine deaminase. The biotinylated probe was hybridized to DNA and mRNA selectively immobilized on nitrocellulose and detected by sequential incubation of the nitrocellulose membrane with avidin and biotinylated polyalkaline phosphatase, followed by colorimetric development. The biotinylated oligonucleotide probe proved useful for the qualitative detection of complementary DNA and mRNA sequences but was unsatisfactory for quantitative determinations using reflective densitometry.

Biotin↗
PubMed1986

Evaluation of a new enzyme-linked immunoassay for terminal deoxynucleotidyl transferase in haematologic malignancies.

We have evaluated a new solid phase enzyme immunoassay (EIA) for detection of terminal deoxynucleotidyl transferase (TDT). The EIA is greater than 100 times more sensitive than previously used tests for enzyme activity. In 284 clinical specimens of human peripheral blood and bone marrow, the EIA detected TdT antigen in 97% of peripheral blood and 100% of bone marrow samples that were positive for enzymatic activity. The excellent sensitivity and specificity of this new test suggests that it can be used in clinical situations where quantitative TdT measurements are desired.

Antigens↗
PubMed1985

Affinity purification and refined structural characterization of terminal deoxynucleotidyltransferase.

A total of 56 stable murine hybridoma monoclones that produce homogeneous antibodies against human or calf terminal deoxynucleotidyltransferase have been established. All of the antibodies exhibited specific binding to various Mr forms of terminal transferase and eight possessed neutralizing activity. Results are presented that permitted characterization of ten of these antibodies with respect to their immunoglobulin class, their recognition of calf or human terminal-transferase Mr species by immunoblotting techniques and their recognition of distinct antigenic sites. Terminal transferase was purified in a single step by using an immunoaffinity column constructed with a monoclonal antibody exhibiting a high binding affinity for the enzyme. Single monoclonal antibodies were also used to bind selectively to terminal-transferase antigen in tissue slices and individual cells.

Animals↗
PubMed1985

Terminal deoxynucleotidyltransferase. Alignment of alpha- and beta-subunits of the core enzyme along the primary translation product.

Terminal deoxynucleotidyltransferase exists in multiple Mr forms, all apparently generated from a single polypeptide of 62kDa. On isolation and purification, the smallest catalytically active protein of this enzyme consists of two subunits, alpha (12kDa) and beta (30kDa). Recently a complementary-DNA nucleotide sequence has been reported for a portion of the enzyme from human lymphoblast. We have pinpointed the locations of the alpha- and beta-subunits within the elucidated nucleotide sequence. From these data, the portions of the nucleotide sequence coding for the catalytically important area of the transferase can be estimated. Here the amino acid sequence of a number of tryptic peptides from calf alpha- and beta-subunits is presented. Because of the striking homology between the amino acid sequence of the calf enzyme and that predicted for human lymphoblast enzyme, it is possible for us to conclude that the alpha-subunit was generated from the C-terminus of the precursor protein and the beta-subunit was non-overlapping and proximal.

Amino Acid Sequence↗
PubMed1985

Terminal deoxynucleotidyl transferase activity in thymocytes of kittens.

Activity of terminal deoxynucleotidyl transferase (TdT) was measured in the thymus of 8- to 14-week-old kittens. Microscopic evidence of involution or other morphologic changes were not observed in formalin-fixed hematoxylin and eosin-stained thymic tissue sections. Thymic tissue from young kittens (8 weeks old) had low TdT activity, as determined by enzymatic catalysis or immunoassay procedures. Markedly higher TdT activity was measured in thymic tissue of older kittens (13 to 14 weeks old). Feline TdT catalyzed the polymerization of deoxynucleotides at a higher rate in Mn2+ than in Mg2+. Results of protein immunoblotting experiments indicated that the major form of feline thymic TdT is a single, high molecular weight polypeptide in 13- to 14-week-old kittens. Detection of TdT activity in the feline thymus indicated that TdT may have the same diagnostic and therapeutic value in feline oncology as in human oncology.

Animals↗
PubMed1985

A new solid-phase immunoassay for terminal deoxynucleotidyl transferase: analysis of TdT antigen in cells, plasma, and serum.

A solid-phase immunoassay for terminal deoxynucleotidyl transferase has been developed using a primary antibody-coated polystyrene bead and secondary antibody conjugated with horseradish peroxidase. The immunoassay was compared with assays for enzyme activity and detection of antigen with immunofluorescence using cells from peripheral blood and bone marrow from patients with leukemia or lymphoma. In each instance, the solid-phase immunoassay correlated correctly with cellular samples judged to be positive by other tests. However, the level of detection of terminal transferase antigen in plasma or serum of patients with leukemia did not reflect accurately the level of terminal transferase in neoplastic cells. The solid-phase immunoassay was greater than 100-fold more sensitive than conventional assays for enzyme activity, rendering it potentially useful for quantitatively monitoring terminal transferase in patients with leukemia.

Antigens↗
PubMed1984

In vitro metabolism of deoxycoformycin in human T lymphoblastoid cells. Phosphorylation of deoxycoformycin and incorporation into cellular DNA.

The biochemical and metabolic effects of deoxycoformycin, a potent inhibitor of adenosine deaminase, were investigated using two human T lymphoblastoid cell lines. A dose-response analysis demonstrated that the concentration of deoxycoformycin at which there was 50% inhibition of growth was greater than 1 X 10(-3) M in lymphoblastoid cells. Uptake of deoxycoformycin was biphasic and occurred much more slowly than for natural nucleosides, and lower saturation levels were reached. The intracellular concentration of deoxycoformycin achieved was 0.4 to 0.5 microM when the extracellular concentration was 1 microM. At 10 microM extracellular concentration, the intracellular concentration was 3-4 microM. Although deoxycoformycin at very low concentrations (1 or 10 microM) did not have any detectable effects on the growth of these cells, the nucleoside was found to be metabolized, and was phosphorylated to give the mono-, di-, and triphosphate derivatives. The triphosphate derivative was incorporated into cellular DNA with little incorporation into cellular RNA. Metabolism of deoxycoformycin in several mutant lymphoblastoid cells deficient in adenosine kinase and/or deoxycytidine kinase was found to be unchanged from wild-type cells, indicating that these major nucleoside kinases do not play a significant role in the phosphorylation of deoxycoformycin. These results may account, at least in part, for the differences that are observed between the pharmacologic inhibition of adenosine deaminase, and the inherited deficiency of adenosine deaminase.

Adenosine Deaminase Inhibitors↗
PubMed1984

Des-gamma-carboxy (abnormal) prothrombin as a serum marker of primary hepatocellular carcinoma.

We detected des-gamma-carboxy prothrombin, an abnormal prothrombin, in the serum of 69 of 76 patients (91 per cent) with biopsy-confirmed hepatocellular carcinoma (the mean level of the abnormal prothrombin was 900 ng per milliliter). In contrast, levels of the abnormal prothrombin were low in patients with chronic active hepatitis (mean, 10 ng per milliliter) or metastatic carcinoma involving the liver (mean, 42 ng per milliliter), and undetectable in normal subjects. In five patients treated with vitamin K there was no reduction in abnormal prothrombin, indicating that its presence was not due to vitamin K deficiency. Surgical resection of tumors in two patients and chemotherapy in one patient markedly reduced abnormal-prothrombin concentrations, which later increased with recurrence of disease. Serum alpha-fetoprotein levels correlated poorly with abnormal-prothrombin levels. Together, the assay for abnormal prothrombin and the alpha-fetoprotein assay identified 64 of 76 patients with hepatoma (84 per cent). Abnormal prothrombin may be useful in the laboratory diagnosis of primary hepatocellular carcinoma.

Aged↗
PubMed1984

Comparison of the native prothrombin antigen and the prothrombin time for monitoring oral anticoagulant therapy.

We have measured the fully carboxylated (native) prothrombin antigen and the undercarboxylated (abnormal) prothrombin antigen in patients treated with sodium warfarin using specific immunoassays to evaluate a new approach for monitoring oral anticoagulant therapy. Plasma and serum samples (391) were assayed for the prothrombin time, native prothrombin antigen, and abnormal prothrombin antigen. The results were correlated with the presence of bleeding or thromboembolic complications at the time of phlebotomy. The native prothrombin antigen correlated with the occurrence of complications in 95% of samples. Of 13 samples from patients with bleeding complications, 13/13 (100%) had a native prothrombin of 12 micrograms/mL or lower. Of seven samples from patients with thromboembolic complications, 6/7 (86%) had a native prothrombin of 24 micrograms/mL or greater. By comparison, a prothrombin time index of 1.5 to 2.5, 1.5 to 2.2, 1.5 to 2.0, or 1.3 to 1.8 identified 6/20 (30%), 9/20 (45%), 11/20 (55%), or 12/20 (60%) patients at risk, respectively. Although the prothrombin time index did correlate with the presence of bleeding complications, the native prothrombin antigen correlated closely with the presence of bleeding and thromboembolic complications. According to these results, the native prothrombin antigen, maintained in a range of 12 to 24 micrograms/mL by regular adjustment of the warfarin dosage, may be associated with a reduced risk of complications due to excessive or insufficient warfarin therapy. On the basis of these preliminary data, we recommend that the native prothrombin antigen be considered to monitor warfarin therapy.

Administration, Oral↗
PubMed1983

Expression of terminal deoxynucleotidyl transferase in human thymus during ontogeny and development.

Expression of the enzyme terminal deoxynucleotidyl transferase (TdT) was studied in human thymus during ontogeny and development. In five fetal thymus samples, the enzyme activity was barely detectable. At birth, the terminal transferase activity remained low. Maximum expression of the enzyme activity occurred between 10 and 40 mo of age. Analysis of six other enzyme activities, adenosine kinase, deoxyadenosine kinase, AMP deaminase, dAMP deaminase, 5' nucleotidase, and adenosine deaminase confirmed the normal status of the thymic tissue. A careful analysis of thymic architecture revealed that involution did not occur as a result of the disease process that necessitated cardiac surgery. By immunofluorescence, the TdT antigen was localized exclusively in the nucleus of cortical thymocytes. Protein immunoblotting studies indicated that human thymic terminal transferase exists as a single high m.w. species in individuals under 30 mo of age. Thereafter, a variant m.w. species is detectable. The increase in expression of this enzyme coincides with the increase observed in serum immunoglobulin levels during maturation and precedes the maximum development of the human thymus.

Adolescent↗
PubMed1983

Adenosine deaminase and terminal deoxynucleotidyl transferase: biochemical markers in the management of chronic myelogenous leukemia.

Serial determinations of adenosine deaminase (ADA) activity in 69 patients with chronic myelogenous leukemia provided a biochemical marker of disease activity. Eighty-nine % of patients in the accelerated phase had an elevation of ADA activity. This elevation was not a direct reflection of an increased absolute blast count. Furthermore, five of seven patients studied serially from the stable phase into the accelerated phase had an increase in ADA activity before the absolute blast count increased. This is the first investigation which clearly demonstrates the potential value of measuring serial ADA activities in a large number of patients with chronic myelogenous leukemia.

Adenosine Deaminase↗
PubMed1982

Deoxynucleotide-interconverting enzymes and the quantification of deoxynucleoside triphosphates in mammalian cells.

We have demonstrated that methanol extracts of human cells are heterogeneous with regard to content of dNDP (deoxynucleoside diphosphate) and dNMP (deoxynucleoside monophosphate) kinases. The presence of these enzymes can affect the reliability of techniques used to measure intracellular pools of deoxynucleotides. An optimized extraction procedure and enzymic assay for dNTP species in haematopoietic cells are described which provide sensitivity to measure 0.1-40pmol of dATP, dTTP and dGTP, and 1.0-40pmol of dCTP. The extraction and assay give linear results with (2.5-15)x10(6) nucleated cells and (0.1-1.5)x10(9) red blood cells. Under these conditions, extracts equivalent to ~0.5x10(6) nucleated haematopoietic cells catalyse the phosphorylation of 0-8% of dNDP and dNMP standards to dNTP and incorporate them into deoxynucleotide polymer under circumstances where 100% of an equimolar dNTP standard would be incorporated. By contrast, extracts of 0.4x10(6) HeLa cells totally converted dADP, dTDP and dGDP into dNTP with subsequent polymerization. Conversion of dCDP was somewhat less efficient. The results demonstrate conclusively that the activities of deoxynucleotide interconverting enzymes differ in different types of human cells. They can interfere with assay of nucleotides, but may not do so in many types of cell extracts. In particular, dNTP concentrations can be measured in human haematopoietic cells after extraction with 60% (v/v) methanol and are not artificially elevated by deoxynucleotide interconversions. It is apparent that extraction and assay procedures for measurement of dNTP species should be analysed for each cell type in order to minimize contaminating enzyme activities and ensure accuracy of dNTP quantification.

Cell Line↗