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Biomedical subjects

R A Clark

Publications and source records attributed to R A Clark.

At least 289 records · Page 16Linked to original sources
PubMed1987

Respiratory burst of normal human eosinophils.

Oxidative metabolism of eosinophils has generally been studied in cells from patients with eosinophilia. We isolated eosinophils with purity of greater than 95% from normal donors. Oxygen metabolism of eosinophils and neutrophils was compared using O2-. production as a measure of the stimulus-induced respiratory burst. During 10 min of stimulation, using phorbol myristate acetate (PMA) or opsonized zymosan (OPZ), eosinophils produced two to three times as much O2-. as did neutrophils. Continuous kinetic analysis was used to measure the latency period and maximal rate of O2-. production. Eosinophils has a shorter latency period and greater rate of O2-. production than did neutrophils at all concentrations of PMA. With OPZ stimulation, O2-. production rates by both cells were similar. The latency periods were similar with high concentrations of OPZ but at limiting amounts of OPZ eosinophils had a longer latency period than did neutrophils. In addition, the kinetic assay demonstrated that the respiratory burst in eosinophils was more sustained than in neutrophils. These results indicate substantial differences in the oxidative burst of eosinophils and neutrophils with respect to activation, capacity, and regulation. These distinctive features of O2-. production by eosinophils may be important in host defense against metazoan parasites or in tissue injury during inflammation.

Dose-Response Relationship, Drug↗
PubMed1987

A once daily theophylline preparation in prevention of nocturnal symptoms in childhood asthma.

Twenty school children with chronic asthma who despite regular prophylactic therapy continued to have troublesome nocturnal wheeze or cough entered a double-blind cross-over study in which a once daily theophylline preparation was compared with placebo to assess control of these symptoms. Seventeen children completed both phases of the study. Significant improvement was noted in the day and night symptom scores, the morning dip index and daily peak flow readings with a significant reduction in rescue bronchodilator inhaler usage during the active treatment period. Satisfactory serum theophylline concentrations were obtained 11-12 h post dose in all children using a standard dose of 18 mg/kg per day at 2000 hours. Three children were withdrawn because of minor side-effects. The theophylline preparation studied in conjunction with other conventional anti-asthma therapy was thus effective in controlling nocturnal symptoms.

Adolescent↗
PubMed1987

Bile duct strictures associated with hepatic arterial infusion chemotherapy.

We report 6 cases of bile duct strictures in patients receiving intraarterial floxuridine chemotherapy for metastatic colon carcinoma. The computed tomographic and cholangiographic features of these cases mimic those seen with primary sclerosing cholangitis. The postulated mechanism for development of biliary strictures is direct toxicity and/or occlusion of the peribiliary vascular plexus with resultant biliary fibrosis.

Bile Duct Diseases↗
PubMed1987

The management of chemotherapy-induced nausea and vomiting.

This paper reviews one of the major side-effects of chemotherapy, emesis. Included are patient and treatment factors that can affect the control of nausea and vomiting as well as a summary of the management of chemotherapy-induced emesis.

Antiemetics↗
PubMed1987

Nucleotide Metabolism in Salt-Stressed Zea mays L. Root Tips: I. Adenine and Uridine Nucleotides.

Corn plants (Zea mays L. cv Pioneer 3906) were grown in a glass house on control and saline nutrient solutions, in winter and summer. There were two saline treatments, both with osmotic potential = -0.4 megapascal but with different Ca(2+)/Na(+) ratios: 0.03 and 0.73. Root tips and shoot meristems (culm tissue) of 26 day-old plants were analyzed for nucleotides to ascertain if there were correlations between nucleotide pool size and the reduced growth on saline cultures. Several other cell components also were determined. Plants grown in winter were only half as large as those grown in summer mainly because of the lower light intensity and lower temperature. But the relative yield reduction on salt treatment compared to the control was similar in winter and summer. The two different salt treatments caused similar yield reductions. Neither salt treatment affected nucleotide pools in culm tissue, with the possible exception of UDPG in winter. In the case of root tips, salt treatment had little or no effect on nucleotide pool sizes in winter when many already seemed near a critical minimum, but in summer it reduced several pools including ATP, total adenine nucleotide, UTP, total uridine nucleotide, and UDP-glucose. The reductions were greatest on the salt treatment with low Ca(2+)/Na(+). There was no simple correlation between the effects of salt stress on growth and on nucleotide pool size. The nucleotide pools of culm tissue indicated that in some respects this tissue was effectively insulated from the salt stress. Roots that were in direct contact with the saline solution indicated significant reductions in nucleotide pools only in the summer whereas growth was reduced both summer and winter. It is possible that the nucleotide concentrations of root cells in winter were already near a critical minimum so that nucleotide synthesis and growth were tightly linked. Significant reductions in nucleotide pools that would be expected to affect growth were more evident in summer when pools were larger and growth was more rapid. But even where ATP and total adenine nucleotides were reduced, the ratio of ATP:ADP and the adenylate energy charge remained unchanged indicating an active adenylate kinase that had access to most of the adenine nucleotide pools, and possible catabolism of excess AMP.

Journal Article↗
PubMed1987

Human keratinocytes synthesize and secrete the extracellular matrix protein, thrombospondin.

Thrombospondin (TSP) a glycoprotein originally identified as the endogenous lectin of platelets, is also synthesized by fibroblasts, endothelial cells, pneumocytes, smooth muscle cells, and macrophages. Thrombospondin is subdivided into functional domains which bind specifically to heparin, fibronectin, collagen, and to specific cellular receptors. It is found within the basement membranes of kidney, lung, smooth muscle, and skin. Thus TSP may serve as an important link between cells and matrices. Thrombospondin also has been reported at the epidermal-dermal junction. We wished to determine whether human keratinocytes synthesize and secrete TSP. Pure human keratinocytes were grown in defined medium without fibroblast feeder layers. Immunofluorescent staining with either rabbit polyclonal or mouse monoclonal antibodies to human platelet TSP yielded specific granular staining within the cytoplasm of keratinocytes. Culture media and cellular lysates were harvested from cultures metabolically labeled with [35S]methionine. Trichloroacetic acid precipitation, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and autoradiography revealed a major labeled band comigrating with purified platelet TSP in both the media and the cellular lysates. Immunoprecipitation with either the polyclonal or the monoclonal anti-TSP antibodies followed by SDS-PAGE and autoradiography identified this band as TSP. Thus keratinocytes in culture synthesize and secrete TSP. Thrombospondin may play an important role in epidermal interactions with extracellular matrix.

Cells, Cultured↗
PubMed1987

Achilles tendon: MR imaging at 1.5 T.

Thirty magnetic resonance (MR) examinations of the Achilles tendon were performed: 20 from patients without suspected tendon abnormalities; ten from patients with suspected tendon abnormalities. The appearance of the normal Achilles tendon is hypointense and flattened. Partial tears appeared as high-signal intratendinous collections, complete acute ruptures appeared as tendinous discontinuity, and uncomplicated surgical repairs appeared as areas of tendinous continuity with inhomogeneous signal in the operative site. Chronic tendinitis appeared as a diffuse thickening of the tendon. MR imaging of the Achilles tendon at 1.5 T enabled the determination of the degree of tendinous continuity, which may help with diagnosis, treatment, and the pacing of rehabilitation.

Achilles Tendon↗
PubMed1987

Comparison of the evolving histopathology of early and late cutaneous and asthmatic responses in rabbits after a single antigen challenge.

Histopathologic changes during the immediate cutaneous response (ICR) and late cutaneous response (LCR) to antigen challenge in allergic humans include dermal edema in the ICR (15 to 30 minutes) followed by increasing cellular infiltration in the LCR (6 hours and more). No description of the evolving histopathologic changes that occur during an immediate asthmatic response (IAR) followed by a late asthmatic response (LAR) exists in either clinical studies or animal models. We examined cutaneous and pulmonary histopathology at 1/2, 6, 24, and 48 hours as well as 7 days after simultaneous intradermal and aerosol antigen challenge of rabbits immunize with Alternaria tenuis extract. Nonimmunized rabbits challenged with Alternaria tenuis extract and immunized rabbits challenged with normal saline served as controls. Immediate wheal and flare responses followed by a LCR were seen in immunized but not control animals. Pulmonary function tests documented immediate and LAR in immunized but not control animals. Thirty minutes after antigen challenge of sensitized animals (ICR and IAR), both dermal sites and large airway submucosal sites had interstitial edema and vessel dilatation while small airways were essentially normal. At 6 hours after challenge, the dermal and large airway submucosal sites of immune animals (LCR and LAR) demonstrated a moderate mixed leukocyte infiltrate as well as residual edema. Additionally, bronchioles and pulmonary vessel adventitia from these responding animals had an intense and widespread leukocyte infiltration. At 24 and 48 hours, immune challenged animals but not controls had a marked mixed cellular infiltrate near skin vessels and near the bronchioles and pulmonary vessels with little or no residual interstitial edema. At 7 days, three of four animals showed resolution of the inflammation while the fourth showed minimal residual changes. Morphometric analysis of airway inflammation substantiated these qualitative observations and demonstrated that the granulocytes around airways of immune rabbits were a mixture of neutrophils and eosinophils at 6 hours, but were predominantly eosinophils at 48 hours. Immunofluorescent studies of skin and lung tissue did not demonstrate any granular or linear deposition of immunoglobulin or complement at the sites of inflammation, however, fibrin deposition was noted in the skin and lungs of immune rabbits. These observations show that immunized rabbits challenged with antigen develop cutaneous and pulmonary inflammation.(ABSTRACT TRUNCATED AT 400 WORDS)

Alternaria↗
PubMed1987

The inflammatory reaction in the airways in an animal model of the late asthmatic response.

The late asthmatic response is defined as airway obstruction that occurs hours after antigen exposure in some atopic asthmatics. The importance of this reaction is that the airway obstruction may be severe, prolonged, and difficult to control unless corticosteroids are employed. In addition, this response may lead to an increase in airway reactivity. To investigate the immunopathogenesis of this disorder, an animal model in rabbits was developed. In this model, antigen-specific IgE was associated with the late asthmatic response and antigen-specific IgG was associated with blunting of the reaction. Antigen challenge of immune rabbits led to edema within the large airways shortly after antigen exposure, with infiltration of inflammatory cells (neutrophils and eosinophils) into the large and small airways during the late response. The infiltrates became more mononuclear with time and resolved over 10 days. As in humans, the late response was associated with an increase in airway reactivity and correlated temporally with infiltration of the airways with neutrophils and eosinophils. The contribution of granulocytic cells to the airway responses to antigen was studied by granulocyte depletion, which prevented both the late response and the heightened airway reactivity. In addition, transfusion of a neutrophil-rich population of white cells into granulocytopenic immune rabbits restored both responses. Thus, in this animal model, the antigen-induced late asthmatic response and subsequent increase in airway reactivity were dependent on the presence of granulocytes at the time of exposure to antigen.

Airway Obstruction↗
PubMed1986

Aberrant activation and regulation of the oxidative burst in neutrophils with Mol glycoprotein deficiency.

Patients whose cells are deficient in the glycoproteins LFA-1, Mol, and p150,95 have recurrent infections and pronounced abnormalities in neutrophil adherence, aggregation, chemotaxis, and phagocytosis. We characterized activation and regulation of oxidative metabolism of Mol-deficient neutrophils. These cells failed to depolarize or to produce O2- or H2O2 normally when stimulated by opsonized zymosan. The chemotactic peptide formyl methionyl-leucyl-phenylalanine depolarized Mol-deficient neutrophils normally but caused supernormal production of O2- and H2O2, a result of a prolonged burst in oxidative metabolism. Phorbol myristate acetate depolarized Mol-deficient neutrophils at a nearly normal rate but evoked release of significantly less O2- and H2O2 than from normal PMN. The aberrant activation and regulation of the oxidative burst in Mol-deficient neutrophils are considered in light of recently emerging concepts in the cell biology of this process, and the possibility that these abnormalities reflect a defect in the cytoskeleton-membrane interaction is discussed.

Cell Adhesion↗
PubMed1986

Oxidative inactivation of pneumolysin by the myeloperoxidase system and stimulated human neutrophils.

Pneumolysin, a hemolytic toxin from Streptococcus pneumoniae, is a member of the group of thiol-activated, oxygen-labile cytolysins produced by various Gram-positive bacteria. The toxin activity of pneumolysin, as determined by lysis of 51Cr-labeled human erythrocytes, was destroyed on exposure to the neutrophil enzyme myeloperoxidase, hydrogen peroxide, and a halide (chloride or iodide). Detoxification required each component of the myeloperoxidase system and was prevented by the addition of agents that inhibit heme enzymes (azide, cyanide) or degrade H2O2 (catalase). Reagent H2O2 could be replaced by the peroxide-generating enzyme system glucose oxidase plus glucose. The entire myeloperoxidase system could be replaced by sodium hypochlorite at micromolar concentrations. Toxin inactivation was a function of time of exposure to the myeloperoxidase system (less than 1 min), the rate of formation of H2O2 (0.05 nmol/min), and the concentration of toxin employed. Toxin that had been inactivated by the myeloperoxidase system was reactivated on incubation with the reducing agent dithiothreitol. Pneumolysin was also inactivated when incubated with human neutrophils (10(5)) in the presence of a halide and phorbol myristate acetate, an activator of neutrophil secretion and oxygen metabolism. Toxin inactivation by stimulated neutrophils was blocked by azide, cyanide, or catalase, but not by superoxide dismutase. Neutrophils from patients with impaired oxygen metabolism (chronic granulomatous disease) or absent myeloperoxidase (hereditary deficiency) failed to inactivate the toxin unless they were supplied with an exogenous source of H2O2 or purified myeloperoxidase, respectively. Thus, inactivation of pneumolysin involved the secretion of myeloperoxidase and H2O2, which combined with extracellular halides to form agents (e.g., hypochlorite) capable of oxidizing the toxin. This example of oxidative inactivation of a cytolytic agent may serve as a model for phagocyte-mediated detoxification of microbial products.

Bacterial Proteins↗
PubMed1986

Immunomodulation by neutrophil myeloperoxidase and hydrogen peroxide: differential susceptibility of human lymphocyte functions.

The coexistence of activated polymorphonuclear leukocytes and lymphocytes in tumor masses and inflammatory tissues suggests the possibility of interaction between secreted neutrophil products and nearby lymphocytes. To test this hypothesis, we examined the effects of neutrophil myeloperoxidase and H2O2 on lymphocytes. Human peripheral blood mononuclear leukocytes were exposed to myeloperoxidase, an H2O2-generating system (glucose + glucose oxidase), and a halide, and were then tested for functional activities. Natural killer activity against K562 cells, lymphocyte proliferation in response to mitogens, and generation of immunoglobulin-secreting cells were all susceptible to oxidative injury by myeloperoxidase and H2O2. The degree as well as the mechanism of suppression was dependent on the glucose oxidase concentration (i.e., the rate of H2O2 delivery). At low H2O2 flux, myeloperoxidase was essential for induction of lymphocyte suppression; as the rate of H2O2 generation increased, suppression became myeloperoxidase-independent and was mediated by H2O2 alone. Various lymphocyte functions were differentially susceptible to oxidative injury by myeloperoxidase and H2O2. The proliferative response to poke-weed mitogen was the least sensitive, whereas antibody formation was the most sensitive. Proliferative responses to concanavalin A and phytohemagglutinin as well as natural killer activity displayed intermediate degrees of susceptibility. In all assays, lymphocyte viability was greater than 90%. Removal of monocytes from mononuclear leukocytes by adherence to glass increased susceptibility of lymphocytes to oxidative injury. Monocytes in proportions within the range present in peripheral blood mononuclear leukocytes protected lymphocyte functions against oxidative injury by myeloperoxidase and H2O2. This study demonstrates a differential susceptibility of various immune functions to oxidative injury by the neutrophil products myeloperoxidase and H2O2, and shows, in addition, that monocytes can modulate these interactions.

Cell Adhesion↗
PubMed1986

Oxidation of lysine side-chains of elastin by the myeloperoxidase system and by stimulated human neutrophils.

Exposure of [3H]-lysine labeled elastin to either purified myeloperoxidase plus H2O2 and halides or human neutrophils plus phorbol myristate acetate resulted in oxidation of lysine side chains quantitated as 3H2O release. In both the enzyme and cell system oxidation was blocked by azide, cyanide or catalase, but not by beta-aminopropionitrile, an inhibitor of lysyl oxidase. Myeloperoxidase-deficient neutrophils were ineffective unless exogenous myeloperoxidase was added. These data provide a biochemical basis for inflammatory changes in connective tissue proteins mediated by oxidant secretory products of neutrophils.

Animals↗
PubMed1986

High-resolution computed tomography of the wrist in patients with carpal tunnel syndrome.

High resolution computed tomography (CT) was used to scan the wrists of 19 patients with idiopathic carpal tunnel syndrome. Thirteen normal volunteers were used as controls. Measurements obtained from the CT images included the cross-sectional area of the carpal tunnel, the relative amount of synovium within the carpal tunnel, the attenuation coefficient of the carpal tunnel, and the thickness of the transverse carpal ligament. No significant difference in any of these measurements was found when comparing the wrists of symptomatic patients with controls. High resolution CT of the wrist does not appear to be of value in the preoperative evaluation of patients with idiopathic carpal tunnel syndrome.

Carpal Bones↗
PubMed1986

Vindesine and mitomycin C in inoperable non-small cell lung cancer.

Twenty-nine patients with inoperable non-small cell lung cancer were treated as out-patients with vindesine and mitomycin C. Eight patients had a complete response, and nine a partial response. Response was generally associated with either stable or improving ECOG and symptom scores. The incidence of serious side-effects was low--only two patients' white cell count fell below 3000 cells/mm2, only one patient's platelet count fell below 100,000 cells/mm2, and two patients developed vomiting associated with treatment. The combination of vindesine and mitomycin C appears to be effective in the treatment of inoperable non-small cell lung cancer. Side effects were generally well tolerated and allowed out-patient treatment.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1986

Microbiological quality of desiccated coconut.

A microbial survey of Sri Lankan desiccated coconut has been made on material purchased in supermarkets in Sheffield or on material obtained directly from the processing company. The total viable count (TVC) was reduced by spoilage and pasteurization from 10(4)/g to 10(3)/g. Most samples contained low levels of coagulase-positive Staphylococcus aureus suggesting that this commodity had been handled during production. One focus of contamination with Aspergillus flavus was found for each 8.34 g of desiccated coconut (mean contamination). The number of bacteria and moulds in spoiled coconut was significantly lower than that in coconut obtained from the processor or purchased from retail outlets. It is suggested that the accumulation of free fatty acids, aliphatic methyl ketones and secondary alcohols produced during fungal spoilage has had a bactericidal and fungicidal effect. The use of microbial specifications for foods is questioned in situations where there is evidence of microbial spoilage having taken place.

Aspergillus flavus↗