PubMed Health⌕ Search

Biomedical subjects

W C Thompson

Publications and source records attributed to W C Thompson.

At least 19 recordsLinked to original sources
PubMed1995

Activated mast cells produce interleukin 13.

When mast cells are activated through their immunoglobulin (Ig)E receptors, release of low molecular weight mediators like histamine is followed by secretion of multiple cytokines, including interleukin (IL)-3, IL-4, IL-5, and granulocyte/macrophage colony-stimulating factor. Here we report that stimulated mast cells also synthesize IL-13 mRNA and protein; secretion of this cytokine may be of particular importance because of its ability to stimulate IgE expression. IL-13 transcripts detected by a semiquantitative reverse transcriptase-mediated polymerase chain reaction assay were induced within 30 min after stimulation of mast cells by dinitrophenyl plus monoclonal IgE anti-dinitrophenyl, and peaked at about 1 h. Within 3 h of IgE stimulation, secreted IL-13 bioactivity, estimated by proliferation of an IL-13-dependent cell line, reached levels equivalent to 1-2 ng/ml of IL-13. When added to human B lymphocytes, the mast cell-derived IL-13 activity (like bone fide IL-13) induced Ig C epsilon transcripts, DNA recombination characteristic of the isotype switch to C epsilon, and the secretion of IgE protein. These results suggest a model of local positive feedback interactions between mast cells and B cells, which could play a role in the pathogenesis of atopy.

Animals↗
PubMed1995

Subjective interpretation, laboratory error and the value of forensic DNA evidence: three case studies.

This article discusses two factors that may profoundly affect the value of DNA evidence for proving that two samples have a common source: uncertainty about the interpretation of test results and the possibility of laboratory error. Three case studies are presented to illustrate the importance of the analyst's subjective judgments in interpreting some RFLP-based forensic DNA tests. In each case, the likelihood ratio describing the value of DNA evidence is shown to be dramatically reduced by uncertainty about the scoring of bands and the possibility of laboratory error. The article concludes that statistical estimates of the frequency of matching genotypes can be a misleading index of the value of DNA evidence, and that more adequate indices are needed. It also argues that forensic laboratories should comply with the National Research Council's recommendation that forensic test results be scored in a blind or objective manner.

DNA↗
PubMed1995

Confirmation and quantitation of cocaine, benzoylecgonine, ecgonine methyl ester, and cocaethylene by gas chromatography/mass spectrometry. Use of microwave irradiation for rapid preparation of trimethylsilyl and T-butyldimethylsilyl derivatives.

The authors developed a technique by which cocaine metabolites as well as cocaethylene can be identified and quantitated using gas chromatography/mass spectrometry (GC/MS), and deuterated standards of benzoylecgonine, cocaine, ecgonine methyl ester, and cocaethylene as internal standards. The authors used a solid phase extraction (Clean Screen, Worldwide Monitoring Corporation, (Horsham, PA)) technique, and rapid derivatization of metabolites using microwave irradiation before GC/MS analysis. The t-butyldimethylsilyl derivatives (prepared by microwave irradiation in 2.5 minutes, 640 Watts [W]) offered better baseline separation and chromatography than conventional trimethylsilyl derivatives. The assay was linear between 0.87-17.3 mumol/L of benzoylecgonine (250-5,000 ng/mL) concentration, 0.83-16.6 mumol/L of cocaine (250-5,000 ng/mL), 0.79-15.8 mumol/L of cocaethylene (250-5,000 ng/mL) and 1.25-25.1 mumol/L of ecgonine methyl ester (250-5,000 ng/mL). The yields are comparable between the microwave technique and conventional heating.

Cocaine↗
PubMed1995

Carbamazepine-salicylate interaction in normal and uremic sera: reduced interaction in uremic sera.

Displacement of phenytoin and valproic acid by salicylate have been described. We studied carbamazepine-salicylate interactions in normal and uremic sera, which have not been studied. Salicylate caused significant displacement of carbamazepine from protein binding, leading to higher concentrations of free carbamazepine. The concentrations of free carbamazepine were always significantly higher in uremic sera than in normal sera. However, when uremic sera were supplemented with both carbamazepine and salicylate, we observed a much lower displacement of carbamazepine and only a slight increase in free carbamazepine concentration. Treatment of uremic sera with activated charcoal corrected the binding deficiency for carbamazepine. Known uremic compounds like hippuric acid and indoxyl sulphate can only partly explain the observed displacement of carbamazepine in uremic sera. We conclude that salicylate displaces carbamazepine from protein binding in normal sera, but this interaction is significantly reduced in uremic sera.

Carbamazepine↗
PubMed1992

The effects of interleukin 2 and alpha-interferon administration on hepatic drug metabolism in mice.

We have administered the cytokines interleukin 2 (IL-2), alpha-interferon (IFN-alpha), and gamma-interferon (IFN-gamma) to mice and measured the alterations in hepatic drug-metabolizing enzyme activities. For comparative purposes and to understand the mechanism of diphtheria and tetanus toxoids and pertussis (DTP) vaccine-induced inhibition of drug metabolism, we also studied the effects of vaccine administration in mice. The administration of IL-2 alone or in combination with IFN-alpha or IFN-gamma causes dose-dependent increases in hexobarbital-induced sleep times. These increases correlate well with the inhibition of specific microsomal mixed-function oxidase activities. Sublethally irradiated mice and athymic nude mice receiving injections of IL-2 or IL-2 plus IFN-alpha do not show the inhibition of drug metabolism seen in normal mice. However, the inhibition of drug metabolism in DTP vaccine-treated mice was similar in all three groups. These observations indicate a possible role for immune cells (probably T-lymphocytes) in the inhibition of drug metabolism caused by administration of these cytokines, which is different from the inhibition of drug metabolism caused by DTP vaccine.

Animals↗
PubMed1992

Thrombin, epidermal growth factor, and phorbol myristate acetate stimulate tubulin polymerization in quiescent cells: a potential link to mitogenesis.

Previous studies suggest that alterations in the microtubule (MT)-tubulin equilibrium during G0/G1 affect mitogenesis. To determine the effect of growth factors on the MT-tubulin equilibrium, we developed a radioactive monoclonal antibody binding assay (Ball et al.: J. Cell. Biol. 103:1033-1041, 1986). With this assay, 3H-Ab 1-1.1 binding to cytoskeletons in confluent populations of cultured cells is proportional to the number of tubulin subunits polymerized into MTs. We now show that purified alpha-thrombin increases 3H-Ab 1-1.1 binding to cytoskeletons of serum-arrested mouse embryo (ME) fibroblasts from 1.5- to 3-fold. This stimulation is dose-dependent and correlates with concentrations of thrombin required for initiation of DNA synthesis. Other mitogenic factors, epidermal growth factor (EGF) and phorbol 12-myristate 13-acetate (PMA), also stimulate MT polymerization. Addition of colchicine (0.3 microM) eight hours after growth factor addition, blocks stimulation of 3H-thymidine incorporation by thrombin, EGF, or PMA, suggesting that tubulin polymerization or subsequent events triggered by MT polymerization are required for cells to enter a proliferative cycle. Consistent with models for autoregulation of tubulin synthesis, thrombin, EGF, and PMA all increase tubulin synthesis 9 to 15 hr after growth factor addition, raising the possibility that the decrease in free tubulin and subsequent stimulation of tubulin synthesis is linked to progression of cells into a proliferative cycle. Colchicine addition to these cells also stimulates DNA synthesis, but colchicine-stimulated cells enter S phase 6 to 8 hr later than those stimulated by growth factors. This delayed stimulation may be related to the time required for degradation of tubulin-colchicine complexes below a critical level. These data suggest that regulation of cell proliferation may be linked to increased MT polymerization and the resulting decrease in free tubulin pools.

Animals↗
PubMed1992

Percutaneous angioplasty for renovascular hypertension due to fibromuscular dysplasia.

Because the cause of hypertension is reversible in only 5 percent of patients, extensive initial work-up should only be considered in selected cases. Secondary causes should be suspected in patients whose hypertension begins before age 30 or after age 50 and in patients whose hypertension suddenly worsens after a long period of good control, becomes severe or malignant, or remains refractory to maximal medical therapy. A sudden reduction in renal function in a hypertensive patient and the discovery of a unilateral small kidney may also raise suspicion of a secondary cause. Renovascular disease, one of the most common secondary causes of hypertension, is usually the result of atherosclerosis in older patients and the result of fibromuscular dysplasia in younger patients. Physical examination seldom contributes to the diagnosis. The classic upper abdominal or flank bruit occurs in only 30 to 50 percent of patients with renovascular disease, and is not uncommon in patients with essential hypertension. The gold standard for diagnosis of renovascular disease remains the arteriogram. Transluminal renal angioplasty may be performed during arteriography if a high-grade stenosis is identified. Other management options include medical therapy and surgical revascularization with grafts.

Adult↗
PubMed1989

Binding kinetics of tetrachloro-1,2-diaminocyclohexaneplatinum (IV) (tetraplatin) and cis-diamminedichloroplatinum (II) at 37 degrees C with human plasma proteins and with bovine serum albumin. Does aquation precede protein binding?

Experiments were conducted at 37 degrees C to study the kinetics of (a) binding of cis-diamminedichloroplatinum (II) (CDDP) and of a racemic mixture of d- and l-isomers of trans-tetrachloro-1,2-diaminocyclohexaneplatinum (IV) [or tetraplatin (TP)] to protein [human plasma proteins or bovine serum albumin (BSA)]; (b) aquation (acid hydrolysis) of CDDP and of TP; and (c) binding of charged (aquated) CDDP species to BSA. The experiments were performed at clinically relevant concentrations for CDDP, so that the proportional concentrations of platinum complexes relative to the concentrations of other chemical species in blood plasma were similar to those obtaining in the clinical use of the drug. "Free" (unbound) platinum complexes were separated from the protein-bound complexes were separated from the protein-bound complexes by gel filtration chromatography. By use of ion-exchange chromatography, charged platinum species were separated from the uncharged species and free charged platinum species of CDDP were separated from those bound to BSA. Platinum in various fractions was quantitated by atomic absorption spectrophotometry with electrothermal atomization; proteins were quantitated by te Bradford method with Coomassie blue dye. The kinetic data obtained by the application of these methods for CDDP are in good agreement with those obtained by other methods, e.g., binding rates based on separations by centrigugal ultrafiltration. The overall protein-binding reaction of CDDP was consistent with a binding process comprising two consecutive first-order reaction steps: the rate-controlling aquation reaction [half-life (t 1/2), approximately 2 hr] followed by a more rapid binding reaction of the charged (aquated) CDDP species to the protein (t 1/2, approximately 23 min). However, the results for TP indicated that prior aquation was not required for protein binding, and we could surmise that binding of TP to protein proceeds via a direct nucleophilic attack. An unexpected finding was the marked, reproducible difference in rates of aquation between the two lots of TP that we used; this finding suggests the need for cautions evaluation of pharmacokinetic data describing the behavior of TP.

Antineoplastic Agents↗
PubMed1987

Monoclonal antibody to the thrombin receptor stimulates DNA synthesis in combination with gamma-thrombin or phorbol myristate acetate.

Studies with various thrombin derivatives have shown that initiation of cell proliferation by thrombin requires two separate types of signals: one, generated by high affinity interaction of thrombin or DIP-thrombin (alpha-thrombin inactivated at ser 205 of the B chain by diisopropylphosphofluoridate) with receptors and the other, by thrombin's enzymic activity. To further study the role of high affinity thrombin receptors in initiation, we immunized mice with whole human fibroblasts and selected antibodies that blocked the binding of 125I-thrombin to high affinity receptors on hamster fibroblasts. One of these antibodies, TR-9, inhibits from 80 to 100% of 125I-thrombin binding, exhibits an immunofluorescent pattern indistinguishable from that of thrombin bound to receptors on these cells, and selectively binds solubilized thrombin receptors. By itself, TR-9 did not initiate DNA synthesis nor did it block thrombin initiation, but TR-9 addition to cells in the presence of alpha-thrombin, gamma-thrombin (0.5 microgram/ml), or PMA stimulated thymidine incorporation up to threefold over controls. In all cases, maximal stimulation was observed at concentrations of TR-9, ranging from 1 to 4 nM corresponding to concentrations required to inhibit from 30 to 100% of 125I-thrombin binding. These results demonstrate that the binding of the monoclonal antibody to the alpha-thrombin receptor can mimic the effects of thrombin's high affinity interaction with this receptor in stimulating cell proliferation.

Animals↗
PubMed1986

A radiolabeled monoclonal antibody binding assay for cytoskeletal tubulin in cultured cells.

To detect changes in the extent of tubulin polymerization in cultured cells, we have developed a radioactive antibody binding assay that can be used to quantitate total cytoskeletal tubulin or specific antigenic subsets of polymerized tubulin. Fibroblastic cells, grown to confluence in multiwell plates, were permeabilized and extracted with 0.5% Triton X-100 in a microtubule-stabilizing buffer. These extracted cytoskeletons were then fixed and incubated with translationally radiolabeled monoclonal antitubulin antibody (Ab 1-1.1), an IgM antibody specific for the beta subunit of tubulin. Specific binding of Ab 1-1.1 to the cytoskeletons was saturable and of a single apparent affinity. All specific binding was blocked by preincubation of the radiolabeled antibody with excess purified brain tubulin. Specific Ab 1-1.1 binding appeared to represent binding to cytoskeletal tubulin inasmuch as: pretreatment of cells with colchicine decreased Ab 1-1.1 binding in a dose-dependent manner which correlated with the amount of polymerized tubulin visualized in parallel cultures by indirect immunofluorescence, taxol pretreatment alone caused an increase in Ab 1-1.1 binding and prevented in a dose-dependent manner the colchicine-induced decrease in antibody binding, in cells pretreated with colcemid and returned to fresh medium, Ab 1-1.1 binding decreased and recovered in parallel with the depolymerization and regrowth of microtubules in these cells, and comparison of maximal antibody binding per cell between primary mouse embryo, 3T3, and human foreskin fibroblasts correlated with immunofluorescence visualization of microtubules in these cells. Thus, this assay can be used to measure relative changes in the level of polymerized cytoskeletal tubulin. Moreover, by Scatchard-type analysis of the binding data it is possible to estimate the total number of antibody binding sites per cell. Therefore, depending on the stoichiometry of antibody binding, this type of assay may be used for quantitating total cytoskeletal tubulin, specific antigenic subsets of cytoskeletal tubulin, or other cytoskeletal proteins.

Animals↗
PubMed1986

CT scanning of lumbar discography. A useful diagnostic adjunct.

Twenty-two patients with continued, undiagnosed symptoms of low back and sciatic pain for an average of 14 months were assessed. Patients studied had prior negative evaluations, including EMG, CT scanning, and/or metrizamide myelography. Three-level, posterolateral, extradural discography was performed on the side opposite the sciatica. One to 6-hours after discography, CT scanning was performed on all injected discs: 91% demonstrated abnormal discograms at one/more levels. CT imaging demonstrated contrast tracking to the periphery of the disc in 82%. Discography reproduced the patient's symptoms in 77%. The direction of contrast tracking seen on scanning correlated with clinical symptoms in 73% and with symptoms at discography in 82%. CT scanning was thought to be a useful adjunct to lumbar discography in patients with prior negative evaluations.

Back Pain↗
PubMed1986

Changes in the extent of microtubule assembly can regulate initiation of DNA synthesis.

We have shown that MT depolymerization by colchicine and other drugs is sufficient to initiate DNA synthesis in serum-free cultures of embryonic fibroblasts and that stabilization of MTs with taxol inhibits this initiation. Growth factors and oncogenic DNA viruses also initiate DNA synthesis by a taxol-sensitive mechanism that appears to require MT depolymerization or rearrangements. Because we have shown that microtubule heterogeneity exists within single fibroblastic cells, we have carried out a series of experiments to determine the extent of microtubule disruption necessary to initiate DNA synthesis. We have compared the effects of various concentrations of colchicine and taxol on initiation of DNA synthesis with their effects on cytoplasmic MT complexes as visualized by indirect immunofluorescence microscopy and quantitated by direct binding of radiolabeled monoclonal antibody to cytoskeletons. The opposing effects of these drugs on MTs shows that there is a correlation between the extent of MT depolymerization and initiation of DNA synthesis. Initiation of DNA synthesis by colchicine in the presence of taxol is half-maximal when taxol and colchicine are added to cultures at a ratio of about 13 to 1. At this drug ratio, taxol stabilizes MTs near the nucleus, but MTs near the cell periphery are depolymerized. Maximal inhibition of DNA synthesis by taxol occurs only at taxol to colchicine ratios where MTs extend throughout the cytoplasm to the cell periphery. Thus, depolymerization of a small fraction of total MTs, particularly those near the periphery, may be sufficient to initiate proliferative events.

Alkaloids↗
PubMed1985

Taxol stabilization of microtubules in vitro: dynamics of tubulin addition and loss at opposite microtubule ends.

We have investigated the effects of taxol on steady-state tubulin flux and on the apparent molecular rate constants for tubulin addition and loss at the two ends of bovine brain microtubules in vitro. These microtubules, which consist of a mixture of 70% tubulin and 30% microtubule-associated proteins (MAPs), undergo a net addition of tubulin at one end of each microtubule (A end) and a precisely balanced net loss of tubulin at the opposite end (D end) at steady state in vitro. They do not exhibit to a detectable extent the "dynamic instability" behavior described recently for MAP-free microtubules, which would be evident as an increase in the mean microtubule length and a decrease in the number of microtubules in the suspensions [Mitchison, T., & Kirschner, M. (1984) Nature (London) 312, 237-242]. We used a double-label procedure in which microtubules were labeled with tritium and carbon-14 at A ends and carbon-14 at D ends to distinguish the two ends, combined with a microtubule collection procedure that permitted rapid and accurate analysis of retention of the two labels in the microtubules. We found that taxol slowed the flux of tubulin in a concentration-dependent manner, with 50% inhibition occurring between 5 and 7 microM drug. The effects of taxol on the apparent molecular rate constants for tubulin addition and loss at the two microtubule ends were determined by dilution analysis at an intermediate taxol concentration. The results indicated that taxol decreased the magnitudes of the dissociation rate constants at the two ends to similar extents, while exerting little effect on the association rate constants.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaloids↗
PubMed1985

Microtubule-associated proteins (MAPs): a monoclonal antibody to MAP 1 decorates microtubules in vitro but stains stress fibers and not microtubules in vivo.

A monoclonal antibody (mAb 7-1.1) was produced against a bovine brain microtubule-associated protein (MAP) preparation that had been separated from tubulin after initial purification by cycles of microtubule assembly and disassembly in vitro. The antibody reacted specifically with two high molecular weight polypeptides of the MAP 1 class, designated MAP 1.1 and MAP 1.2, and also with the surfaces of MAP 1-containing microtubules that had been assembled in vitro. Double immunofluorescence microscopy using mAb 7-1.1 and a well-characterized rabbit anti-tubulin antibody revealed that mAb 7-1.1 stained stress fibers in fixed and permeabilized cultured mammalian cells rather than microtubules. The antibody also stained cell nuclei in a punctate fashion. mAb 7-1.1 is one of a number of monoclonal antibodies that react with presumptive MAP 1 polypeptides. Some of the MAP 1 antibodies have been found to bind specifically to microtubules in fixed and permeabilized cells, while others have been reported to react with nonmicrotubule structures. Our results, together with the results of other investigations, indicate that "MAP 1" may be a family of several high molecular weight polypeptides that adventitiously behave as MAPs by the criterion of in vitro coassembly with tubulin through cycles of polymerization and depolymerization but whose cellular distributions, and perhaps functions, are varied.

Animals↗