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R A Bray

Publications and source records attributed to R A Bray.

85 records · Page 5Linked to original sources
PubMed1986

Role of lipoxygenation in human natural killer cell activation.

Nordihydroguaiaretic acid (NDGA), quercetin, eicosatetraynoic acid (ETYA), phenidone, and esculetin, agents known to inhibit cellular lipoxygenase (LO) activity, also inhibit human natural killer cell-mediated cytotoxicity (NK-CMC) of K562 tumor target cells (TC) in a dose-dependent fashion. Kinetic analysis demonstrated that LO inhibitors blocked an early event in the activation of the lytic mechanism but did not impair conjugate formation. LO inhibitors also did not affect subsequent chromium release, indicating that their site of inhibition was the NK cell and not the TC. The lipoxygenase products 5-hydroperoxyeicosatetraenoic acid (5-HPETE) and leukotriene-B4 significantly enhanced NK activity, with 5-HPETE being the more effective. Other LO products tested included 15-HPETE and the hydroxy derivatives 15-hydroxyeicosatetraenoic acid (15-HETE) and 5-HETE. These LO metabolites were either without effect on NK-CMC or inhibitory, depending upon the concentration. Additionally, we examined the ability of 5-HPETE to circumvent the effects of LO inhibitors and found that, in the presence of NDGA, ETYA or quercetin, 5-HPETE significantly (p less than 0.001) restored lytic activity. Inhibitors of LTB4 and LTC4 synthesis, diethylcarbamazine and U-60,257 respectively, produced no inhibition of NK activity. In fact, U-60,257 significantly (p less than 0.05) enhanced NK-CMC. Previous studies in our laboratory, with a new technique which allows for the separation of NK cells from K562 cells, have shown that K562-treated effector cells are greater than 90% inactivated when retested against fresh K562 in the standard chromium release assay. Lipids were extracted from K562-treated, Percoll-purified LGL and evaluated by thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC). No significant increases were seen in the arachidonic acid-derived LO products evaluated. Thus, our studies indicate that lipoxygenation may be required in the activation of NK-CMC, possibly as a means to generate oxygen radicals which have been previously implicated in NK-CMC.

Arachidonic Acid↗
PubMed1985

Evidence for an early calcium-independent event in the activation of the human natural killer cell cytolytic mechanism.

In this study, we examined the functional status of human natural killer (NK) cells after their direct interaction with the NK-sensitive tumor target cell (TC), K562. Human peripheral blood lymphocytes depleted of adherent cells were incubated for 4 hr with unlabeled K562 cells at an effector cell (EC) to TC ratio of 2:1. After incubation, the EC were separated from the TC via centrifugation over a single-step Percoll gradient. K562-treated and separated EC were subsequently shown to be unable to lyse fresh K562 TC when retested in the standard chromium-release assay. Kinetic studies revealed that greater than 90% inactivation of NK cell-mediated cytotoxicity (CMC) could be achieved within 2 hr. Inactivation of NK-CMC by K562 was not caused by a specific loss of NK cells, as detected by changes in the expression of two NK cell-associated markers, Leu-7 and Leu-11, or to alterations in EC viability and target binding cell capacity. Interestingly, NK inactivation also occurred in medium devoid of extracellular calcium, although parallel testing of NK-CMC in the same medium resulted in no chromium release. NK inactivation, however, was significantly prevented when the EC and TC were co-incubated at 4 degrees C, or in medium without magnesium. Additional studies revealed that inactivation of NK-CMC could be achieved with another NK-sensitive, but not with an NK-resistant TC. Overall, we demonstrated that NK cells rapidly lost their lytic potential after direct interaction with a sensitive TC, although the cells remained viable, expressed the same percentage of Leu-7 and Leu-11, and could still bind the TC; and NK inactivation occurred in the absence of extracellular calcium, but not when EC and TC were incubated in medium without magnesium. These latter results provide evidence for an early event in the activation of human NK cells that is binding dependent, temperature sensitive, and independent of extracellular calcium.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1983

Mechanism of action of phorbol myristate acetate on human natural killer cell activity.

We have investigated the kinetics of inhibition and regeneration of human natural killer (NK) cell-mediated lysis of K562, a human erythroleukemia cell line, by the potent tumor-promoting agent phorbol-12-myristate-13-acetate (PMA). It is shown that PMA inhibits NK cell-mediated cytotoxicity (CMC) in a dose-dependent manner whether the compound is present throughout the 4-hr cytotoxic assay or the effector cells (EC) are pretreated with PMA. Pretreatment of the target cells (TC) with PMA produced a different profile of NK activity suggesting that PMA inhibition of NK-CMC is primarily due to the inactivation of EC. PMA-induced inhibition of NK-CMC does not affect TC binding and is not circumvented by compounds that enhance intracellular levels of cyclic guanosine monophosphate (cGMP) or calcium. Furthermore, and contrary to a recent report, PMA-induced inhibition of NK-CMC is independent of monocytes. Finally, kinetic studies revealed that PMA-induced inhibition of NK-CMC occurs rapidly and is fully reversible provided that "regenerated EC" are thoroughly washed, prior to the cytotoxic assay, to rid the cell suspension of residual PMA. The potential implications of these results to the currently accepted theory of TC destruction by NK cells, the stimulus-secretion model, are discussed.

Calcimycin↗
PubMed1978

Two new species of Enenterum Linton, 1910 (Digenea) in the marine fish Neoscorpis lithophilus (Kyphosidae) from the south-western Indian Ocean.

Enenterum elsti sp. nov. and E. prudhoei sp. nov. are described from the intestine of Neoscorpis lithophilus off Mapelane, Natal, South Africa. These species differ from others of the genus Enenterum in the ratio of oral sucker to body-length and in the length of the prepharynx. E. elsti differs from E. prudhoei in size, in sucker-ratio and in the number and configuration of the oral lobes. A key to the species of Enenterum is presented and the status of the genus briefly discussed.

Animals↗
PubMedDate not supplied

Low incidence of red cell and HLA antibody formation by bone marrow transplant patients.

BACKGROUND: Bone marrow transplant (BMT) patients, although immunosuppressed, are at risk for the development of red cell (RBC) and HLA antibodies, and they often are given filtered blood in an effort to prevent the latter complication. This study attempts to determine the rate of formation and the specificity of both RBC and HLA alloantibodies in this patient population. STUDY DESIGN AND METHODS: BMT patients (148 received autologous marrow; 45 received allogeneic marrow) from an 18-month period, including patients with leukemia (57 patients), lymphoma (54), breast cancer (68), myeloma (8), myelodysplastic syndrome (5), and aplastic anemia (1), were studied to determine the rate of alloantibody formation to RBC and HLA antigens. A total of 2,410 RBC antibody screens were performed. The patients received 3,921 packed RBCs and 5,915 single-donor platelet units; all were irradiated and administered via white cell-reduction filters. RESULTS: Seven (3.6%) of 193 patients had RBC antibodies upon hospital admission. Four (2.1%) of 193 developed RBC antibodies during the course of BMT: 3 patients had one RBC antibody and 1 patient had two RBC antibodies. RBC antibodies included anti-E (n = 2), anti-M (n = 1), anti-Jkb (n = 1), and anti-Lu14 (n = 1). Thus, 98 percent of patients (189/193) did not develop new (182/186) or additional (7/7) RBC antibodies during BMT. BMT patients were also screened weekly for HLA antibody formation (60-cell panel). Upon admission, 170 (85%) patients were negative. Of these, 8 (4.7%) developed persistent HLA antibodies (mean panel-reactive antibody score, 33 +/- 29%) and 9 (5.3%) were variably positive. Thus, in our setting and population, RBC antibody formation was 0.1 percent per unit transfused, and the HLA alloimmunization rate was 5 to 10 percent. CONCLUSION: As RBC antibody screens are done every Monday, Wednesday, and Friday on this BMT service and as RBC antibody formation is low in these patients, screening for unexpected antibodies might be possible on a more infrequent basis. Also, the rate of HLA alloimmunization in this population receiving filtered blood components is low.

Adult↗
PubMedDate not supplied

A survey of gastrointestinal helminths of the common helmet guinea fowl (Numida meleagris galeata) in Burkina Faso.

Guinea fowls in Burkina Faso (Africa) harbored 13 species of helminth parasites. The two most abundant species were Subulura suctoria and Ascaridia numidae, which comprised 89% of the nematodes. The other nematode species (Gongylonema congolense, Eucoleus annulatus, Synhimantus spiralis, Tetrameres fissispina, and Cyrnea parroti) occurred at low levels. Five species of cestodes and one acanthocephalan were also present. It is likely that guinea fowl act as important reservoir hosts of chicken nematodes.

Africa↗