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Biomedical subjects

L L Thomas

Publications and source records attributed to L L Thomas.

At least 55 records · Page 3Linked to original sources
PubMed1987

Endotoxin testing in blood.

A chromogenic assay is presented for the determination of endotoxin (LPS) in blood. The assay is based upon the LPS-dependent activation of Limulus amebocyte lysate (LAL), and the subsequent measurement of the activated enzyme with a chromogenic substrate. Handling and stability of the reagents, details of the assay method in tubes or microtiter-plates, recovery of LPS from spiked blood in platelet-rich plasma (PRP), platelet-poor plasma (PPP) and serum, as well as the possibility to store plasma samples will be discussed. A clinical evaluation of the assay is provided by S. van Deventer et al. in this volume.

Chromogenic Compounds↗
PubMed1986

A flow cytometric procedure for the isolation of antigenically responsive human basophils.

A flow cytometric procedure is described for the isolation of human basophils. The basophils are isolated by cell sorting after passive sensitization with mouse FITC-IgE anti-DNP, and the isolated basophils exhibit characteristic histamine release in response to incubation with DNP21-human serum albumin conjugates. Using this method, 1-4 X 10(5) basophils can be isolated at greater than or equal to 98% purity from approximately 30 ml whole blood in a 2 h sorting procedure.

Basophils↗
PubMed1986

Characterization of cyclic-nucleotide phosphodiesterase activities in resting and N-formylmethionylleucylphenylalanine-stimulated human neutrophils.

Cyclic nucleotide phosphodiesterase activities in human neutrophils were characterized. Neutrophil sonicates exhibited high-affinity and low-affinity cAMP phosphodiesterase activities, with apparent Km values of 1.9 microM and 112 microM, respectively. No cGMP phosphodiesterase activity was detected. Approx. 70% of cAMP phosphodiesterase activity measured at 1 microM cAMP was present in the soluble subcellular fraction, and the remainder was localized in the particulate fraction. Chromatography of the soluble subcellular fraction on DE-52 ion-exchange resin yielded a low-affinity cAMP phosphodiesterase activity and a high-affinity cAMP phosphodiesterase activity. The soluble high-affinity cAMP phosphodiesterase activity exhibited moderate calmodulin sensitivity. After incubation of intact neutrophils with N-formylmethionylleucylphenylalanine (fMet-Leu-Phe), a 25-30% increase in the activity of the high-affinity cAMP phosphodiesterase activity was observed in the sonicate and in the soluble fraction. Maximal increases were achieved after 2 min of incubation and the increases persisted for at least 10 min. The increase in activity was independent of calmodulin and guanine nucleotide regulatory proteins. These results indicate that a soluble high-affinity cAMP phosphodiesterase comprises the majority of phosphodiesterase activity in neutrophils and that increases in this activity may contribute to the regulation of cAMP levels in neutrophils during activation.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1986

Potentiation of human basophil histamine release by protamine: a new role for a polycation recognition site.

Protamine is an arginine-rich basic polypeptide that stimulates histamine release from rat mast cells but not from human basophils. In this report, we show that protamine causes a non-cytolytic potentiation of IgE-mediated histamine release from human basophils. A direct effect of protamine on basophils was supported by results obtained using cell preparations containing 35-65% basophils. The potentiation occurred at all concentrations of antigen that initiated release and was most pronounced at antigen concentrations that alone stimulated minimal histamine release. The kinetics of potentiated release were parallel to those for IgE-mediated histamine release, and addition of protamine did not overcome the block caused by antigenic desensitization. Staging experiments indicated that enhancement occurred only when protamine and antigen were added together in a single step reaction. Protamine also potentiated release stimulated by eosinophil granule major basic protein or poly-L-lysine, but inhibited release initiated by poly-L-arginine; poly-L-arginine stimulated release was also inhibited by polymyxin B. Arginine-rich histone mimicked the protamine effect, while lysine-rich histone, polymyxin B, and compound 48/80 had minimal or no effect on IgE-mediated release. These results suggest that a polycation recognition site on human basophils similar to that described for rat mast cells may mediate potentiation of basophil secretory events by arginine-rich basic polypeptides.

Basophils↗
PubMed1985

Interrelationships of locus of control content dimensions and hopelessness.

Items from three locus of control (LOC) tests and the Beck Hopelessness Scale were administered to 197 college students. Factor analyses produced multiple factors for each LOC test, but the Beck scale proved to be unidimensional. Factor scales were constructed for each test, and scores were factor analyzed to discover common content. Each LOC test contained a salient dimension that described belief in luck, chance, or fate, and corresponding scales were well correlated. Internal control was the second common theme, with variations according to whether control was attributed to oneself or to people in general. The third common component expressed a personal helplessness or powerlessness. Each common factor was loaded by the Hopelessness Scale, which also correlated with all but one LOC factor scale.

Factor Analysis, Statistical↗
PubMed1985

High school students' long-term retention of sex education information.

Ninth grade students in a rural South Carolina school were pretested about sexuality information, completed a 12-unit reproductive health course in eight months, and were posttested. A control group received the same pretest and posttest. Both groups were retested after the 10th and 11th grades and mean scores were calculated and compared. The difference between the experimental group's pretest and posttest mean scores was 8.49 (p less than .001); the difference between the control group's pretest and posttest mean scores was 1.0 (p = .003). The experimental group's mean score remained at least 5.2 points higher (p less than .001) than the control group's score on the same test one and two years after the course. Comparison of the mean gain between the pretest and posttest scores, and between the pretest and fourth test scores, confirmed the results obtained by mean test scores. The test scores indicated that the knowledge of the experimental students increased significantly and was sustained for two years. Their scores remained significantly higher than those of the control group on the posttest, and on tests one and two years later.

Adolescent↗
PubMed1985

Donor sensitivity to basophil activation by eosinophil granule major basic protein.

Leukocytes of 22 individuals were incubated with a suboptimal concentration of eosinophil granule major basic protein and the amount of histamine release was determined. Cells from 20 of the 22 donors had a histamine release of greater than or equal to 15%. The use of selected donors on repeated occasions revealed significant variability in individual donor responsiveness. The findings support a role for major basic protein activation of human basophils in allergic reactions.

Basophils↗
PubMed1985

Optimalization of a chromogenic assay for endotoxin in blood.

Early detection of Gram-negative septicemia or endotoxemia may become feasible with sensitive and reliable endotoxin (LPS) measurements. We recently published an assay for LPS in blood, based upon the LPS dependent activation of Limulus amebocyte lysate (LAL) and the subsequent chromogenic measurement of the activated enzyme(s). Inhibitors and activated clotting factors potentially interfering in the assay were removed by dilution and heating. In the present study we describe the further improvement of the assay. Optimal conditions include: blood anticoagulated with 30 I.U./ml heparin; dilution of the platelet-rich plasma (PRP) in water; 5 min. heating at 75 degrees C; 15 mM Mg2+, 1.5 mM Ca2+, 125 mM Na+, 50 mM TRIS, pH 8.5 in the LAL activation step; substrate step without extra addition of Ca2+, Mg2+, or Na+, but in the presence of 50 mM TRIS at pH = 9.5. Under those optimal conditions less than 10 pg LPS per ml blood (PRP) can easily be detected. Prospective clinical trials are presently envisaged to investigate the clinical usefulness of this extremely sensitive LPS assay.

Chromogenic Compounds↗
PubMed1985

Validity of the endotoxin assay in post surgical patients.

In a prospective study 56 patients were studied after major surgery for 10 days to correlate endotoxemia with bacteremia and clinical septicemia. Endotoxemia was detected with a quantitative plasma endotoxin assay using limulus lysate and a chromogenic substrate. Clinical septicemia was defined using a set of predetermined criteria. In 29 patients both bacterial cultures and endotoxin assays were negative. One patient showed clinical signs of septicemia. In 14 patients, low grade endotoxemia (mean 47 +/- 15 pg/ml) was observed in the first three days after surgery. Only three of these patients also showed positive endotoxin tests after this period. Corresponding blood cultures were frequently negative (81%) most likely due to prior and concurrent antibiotic prophylaxis. Two endotoxin positive patients had clinical signs of septicemia. In a total of 16 patients, including two patients from the former group endotoxemia (mean 56 +/- 21 pg/ml) was noted beyond the third post-operative day. Samples for blood cultures collected simultaneously were positive for gram negative bacilli in six patients. Clinical septicemia was present in 12 of the 16 patients. The positive and negative predictive value of the endotoxin test for bacteremia and/or septicemia after the third day of surgery for all patients was found to be 75% and 98% respectively. The results of this small prospective study in surgical patients suggest that this rapid endotoxin test is a useful clinical adjunct for both the detection and exclusion of gram negative bacteremia/septicemia.

Adult↗
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↗
PubMed1984

Effect of the calcium ionophore A23187 and aspirin on histamine release in vitro from leukocytes of aspirin-intolerant donors.

In vitro histamine release from leukocytes of 10 aspirin-intolerant donors in response to the calcium ionophore A23187 and aspirin was compared to that of controls. Incubation with A23187 induced a concentration-dependent histamine release from leukocytes of all donors. At 0.1 and 0.2 micrograms/ml A23187, release from leukocytes of aspirin-intolerant donors was significantly less (p less than 0.01) than that of controls. Preincubation with aspirin failed to alter spontaneous or A23187-stimulated histamine release. Leukocytes of aspirin-intolerant donors do not demonstrate an enhanced sensitivity to histamine release stimulated by aspirin or A23187.

Adult↗
PubMed1984

Stimulation of basophil and rat mast cell histamine release by eosinophil granule-derived cationic proteins.

Major basic protein (MBP), an arginine-rich basic polypeptide that constitutes the crystalloid core of the large specific eosinophil granule, has previously been shown to stimulate noncytolytic histamine release from human basophils and rat mast cells by an IgE-independent mechanism. Two additional basic polypeptides present in eosinophil granules, eosinophil cationic protein (ECP) and eosinophil-derived neurotoxin (EDN), were examined for similar activity in the present study. Acid-solubilized eosinophil granules were fractionated by chromatography on a Sephadex G-50 column. Incubation of basophil-containing human mononuclear cells with the individual column fractions demonstrated that histamine release occurred only with the fractions that contained MBP. The selectivity of the basophil response for MBP was confirmed by using equimolar concentrations of purified MBP, ECP, and EDN. In contrast, both MBP and ECP, but not EDN, stimulated histamine release from purified rat peritoneal mast cells. Reduction and alkylation of the MBP molecule diminished the response of human basophils to MBP but enhanced the potency of the molecule with rat mast cells. The distinct potency of MBP as a stimulus for histamine secretion from human basophils suggests that eosinophil release of MBP may be a specific event in the augmentation of immediate hypersensitivity reactions and other disorders characterized by eosinophilia.

Animals↗
PubMed1983

Activation of basophil and mast cell histamine release by eosinophil granule major basic protein.

Major basic protein (MBP) is a primary constituent of eosinophil granules. In this report, we demonstrate that MBP from human eosinophil granules initiates a nonlytic histamine release from human leukocytes. A direct effect of MBP on basophils was confirmed using purified human basophils. The kinetics of release were similar to those reported for poly-L-arginine, although MBP was less potent than poly-L-arginine of similar molecular weight. Reduction and alkylation of MBP diminished both the potency and efficacy of the molecule. Native MBP also stimulated histamine secretion from purified rat peritoneal mast cells in a manner characteristic of other polycations. These results emphasize the bidirectional nature of the basophil/mast cell-eosinophil regulatory axis.

Animals↗
PubMed1982

Massive vincristine overdose: failure of leucovorin to reduce toxicity.

The case history of a 24-year-old male with the nodular sclerosing form of Hodgkin's disease (stage IIE) who accidentally received an overdose of vincristine (25 mg, 0.39 mg/kg) is reported. To date, ten patients given a vincristine overdose have been reported. Two of those patients were treated with leucovorin. One patient died after 68 hours. In the second patient, the time to onset and the duration of symptoms were shortened. In an attempt to reduce the duration of toxic effects in our patient, leucovorin was administered 24 hours after the overdose. In agreement with the earlier observation, the time to onset of symptoms was short, but in contrast we did not find a more rapid recovery from the serious side effects. Although the patient might have died without leucovorin administration, we believe its beneficial effect remains to be established.

Adult↗