Biomedical subjects

A D Bankhurst

Publications and source records attributed to A D Bankhurst.

At least 19 recordsLinked to original sources

PubMed2005

A randomised controlled trial of the reciprocating syringe in arthrocentesis.

OBJECTIVE: To evaluate the outcomes of arthrocentesis with the new highly controllable, one handed reciprocating procedure syringe compared with a conventional syringe. METHODS: 100 arthrocentesis procedures were randomised between the reciprocating syringe and the conventional syringe. Outcome measures included patient pain, procedure duration, operator satisfaction, synovial fluid volume, cell counts, and complications. RESULTS: 50 arthrocentesis procedures with the conventional syringe resulted in a mean (SD) procedure time of 3.39 (1.88) minutes, a mean VAPS (patient pain) score of 5.35 (3.15), and a mean VASS (operator satisfaction) score of 4.88 (1.92); 30 of the 50 subjects experienced moderate to severe pain (VAPS score 5 or greater) during arthrocentesis. In contrast, the reciprocating syringe resulted in a reduced procedure time of 1.94 (1.14) minutes (p<0.001), a reduced VAPS (patient pain) score of 2.54 (1.60) (p<0.001), and an increased VASS (operator satisfaction) score of 8.91 (0.79) (p<0.001). Only five of the 50 of subjects experienced moderate to severe pain with the reciprocating syringe. Synovial cell counts were similar between the two syringes (p>0.05), but there was a trend toward greater volume (greater synovial fluid yield) and fewer red blood cells with the reciprocating syringe. CONCLUSIONS: Arthrocentesis with a conventional syringe results in moderate to severe pain in 60% of subjects. The reciprocating syringe prevents significant pain, reduces procedure time, and improves physician performance of arthrocentesis. The reciprocating syringe is superior to the conventional syringe in arthrocentesis.

Adult↗

PubMed1999

A trial of etanercept, a recombinant tumor necrosis factor receptor:Fc fusion protein, in patients with rheumatoid arthritis receiving methotrexate.

BACKGROUND: Patients treated with methotrexate for rheumatoid arthritis often improve but continue to have active disease. This study was undertaken to determine whether the addition of etanercept, a soluble tumor necrosis factor receptor (p75):Fc fusion protein (TNFR:Fc), to methotrexate therapy would provide additional benefit to patients who had persistent rheumatoid arthritis despite receiving methotrexate. METHODS: In a 24-week, double-blind trial, we randomly assigned 89 patients with persistently active rheumatoid arthritis despite at least 6 months of methotrexate therapy at a stable dose of 15 to 25 mg per week (or as low as 10 mg per week for patients unable to tolerate higher doses) to receive either etanercept (25 mg) or placebo subcutaneously twice weekly while continuing to receive methotrexate. The primary measure of clinical response was the American College of Rheumatology criteria for a 20 percent improvement in measures of disease activity (ACR 20) at 24 weeks. RESULTS: The addition of etanercept to methotrexate therapy resulted in rapid and sustained improvement. At 24 weeks, 71 percent of the patients receiving etanercept plus methotrexate and 27 percent of those receiving placebo plus methotrexate met the ACR 20 criteria (P<0.001); 39 percent of the patients receiving etanercept plus methotrexate and 3 percent of those receiving placebo plus methotrexate met the ACR 50 criteria (for a 50 percent improvement) (P<0.001). Patients receiving etanercept plus methotrexate had significantly better outcomes according to all measures of disease activity. The only adverse events associated with etanercept were mild injection-site reactions, and no patient withdrew from the study because of adverse events associated with etanercept. CONCLUSIONS: In patients with persistently active rheumatoid arthritis, the combination of etanercept and methotrexate was safe and well tolerated and provided significantly greater clinical benefit than methotrexate alone.

Adult↗

PubMed1999

Lysophosphatidylcholine and arachidonic acid are required in the cytotoxic response of human natural killer cells to tumor target cells.

Treatment of human natural killer (NK) cells with phospholipase A(2) (PLA(2)) inhibitors, mepacrine and 4-bromophenacyl bromide (BPB), diminished their ability to lyse K562 target cells by as much as 100%. The ability of NK cells to bind to K562 cells was significantly affected by BPB above 2 microM, but not by mepacrine at any concentration tested. This indicates that BPB is having effects on NK cells unrelated to its inhibition of PLA(2) activity at concentrations above 2 microM. The activation of phospholipase C in response to K562 cell binding (as measured by inositol phosphate turnover) was unaffected by inhibition of the PLA(2) activity. The products of PLA(2) catabolism are a fatty acid (often arachidonic acid) and a lysophospholipid. Inhibition of NK cytotoxicity by mepacrine or BPB is reversed significantly when lysophosphatidylcholine, but no other lysolipid, is added back to the NK cells before assaying for cytotoxicity. Arachidonic acid, but not linoleic acid, also significantly reverses inhibition of NK cytotoxicity. Finally, the 15-lipoxygenase product, 15S-hydroperoxyeicosatetraenoic acid (15S-HPETE), is also able to reverse mepacrine-induced inhibition of NK cytotoxicity. The 5-lipoxygenase product 5S-HPETE was not effective. These data indicate that PLA(2) activation is a necessary signal in human NK cytotoxicity and that it is not involved in protein tyrosine kinase and subsequent phospholipase C activation; these latter two enzymes are also required in the cytotoxic response. Thus PLA(2) activation is either a more distal signal, dependent on activation of some earlier signal, or an independent cosignal stimulated by tumor-target binding which generates lysophosphatidylcholine, arachidonic acid, and/or a lipoxygenase product(s).

Acetophenones↗

PubMed1996

EBT, a tryptophan contaminant associated with eosinophilia myalgia syndrome, is incorporated into proteins during translation as an amino acid analog.

The tryptophan dimer 1,1'-ethylidenebis[L-tryptophan] was identified as a contaminant of tryptophan preparations associated with Eosinophilia-Myalgia Syndrome. In this paper, we describe experiments examining the hypothesis that 1,1'-ethylidenebis[L-tryptophan] acts as an amino acid analog replacing L-tryptophan during the synthesis of proteins. We propose further that proteins containing 1,1'-ethylidenebis[L-tryptophan] are rejected in an autoimmune process identified clinically as Eosinophilia-Myalgia Syndrome. Rabbit reticulocyte lysates containing an estimated 1 microM L-tryptophan were used to assay the ability of 1,1'-ethylidenebis[L-tryptophan] to compete with 3H-L-tryptophan for incorporation into proteins translated from BMV RNA. 1,1'-Ethylidenebis[L-tryptophan] in concentrations of 40, 80 and 110 microM reduced lysate 3H-L-tryptophan incorporation to 81%, 76% and 75% of control incorporation obtained in the absence of 1,1'-ethylidenebis[L-tryptophan]. In the presence of 20 microM L-tryptophan, 110 microM 1,1'-ethylidenebis[L-tryptophan] reduced 3H-L-tryptophan incorporation to 56% of control incorporation. In contrast, ethyl-L-tryptophan did not significantly reduce 3H-L-tryptophan incorporation. In the presence of 110 microM 1,1'-ethylidenebis[L-tryptophan] and 20 microM L-tryptophan, 3H-L-leucine incorporation was not significantly reduced compared to incorporation in the absence of 1,1'-ethylidenebis[L-tryptophan], demonstrating that proteins were translated to full length during elongation. These findings suggest that 1,1'-ethylidenebis[L-tryptophan], but not ethyl-L-tryptophan, reduced 3H-L-tryptophan incorporation into proteins by substituting for L-tryptophan rather than by causing premature termination or significant slowing of nascent protein chains.

Animals↗

PubMed1993

Phospholipase C activation in the cytotoxic response of human natural killer cells requires protein-tyrosine kinase activity.

Treatment of highly purified natural killer (NK) cells with the protein-tyrosine kinase (PTK) inhibitors, genistein and herbimycin A, diminished their ability to lyse K562 target cells by as much as 100%. The ability of NK cells to bind to K562 cells was not affected by PTK inhibition. However, activation of phospholipase C (PLC) in response to K562 cell binding (as measured by inositol phosphate turnover) was decreased by as much as 75% when PTK activity was inhibited. Furthermore, there was an increase in tyrosine phosphorylation of NK cell PLC gamma 2 after exposure to K562 target cells. These data indicate that a PTK is involved in the activation of NK PLC by tumour target cells in the cytotoxic response.

Benzoquinones↗

PubMed1992

Effects of pertussis toxin treatment on human natural killer cell function.

Membranes from highly purified natural killer (NK) cells were ADP ribosylated by treatment with pertussis toxin (PTX). PTX treatment resulted in a single band of 32P incorporation at M(r) 41,600. PTX treatment of NK cells diminished their ability to lyse K562 tumour cells by about 50%. However PTX treatment had no measurable effect on cAMP levels in NK cells. PTX pretreatment also had no effect on the ability of target cells to induce phosphoinositide turnover or on the ability of the NK cells to conjugate with the K562 tumour cells. Movement toward the chemoattractants interleukin-2 (IL-2) and formylmethionylleucylphenylalanine (FMLP) was significantly inhibited indicating that a PTX substrate in NK cells may be involved in the transduction of signals which are involved in cell motility.

Cell Adhesion↗

PubMed1990

Effects of beta-adrenergic receptor activation, cholera toxin and forskolin on human natural killer cell function.

Membranes from highly purified natural killer (NK) cells were ADP-ribosylated by treatment with cholera toxin (CTX). CTX resulted in a single band of specific 32P incorporation at Mr 43,600. CTX treatment of intact NK cells caused a 9-fold increase in cyclic AMP (cAMP) concentrations. Pretreatment of NK cells with CTX diminished their ability to lyse K562 tumour cells by up to 79%. Forskolin treatment elevated NK cell cAMP levels 8-fold and decreased lysis of K562 cells by up to 45%. Adrenaline and isoprenaline (isoproterenol) both inhibited lysis of K562 cells by approx. 35% and elevated cAMP by at least 2.5-fold, and their inhibition of lysis was reversed by propranolol. These data suggest that the stimulatory guanine-nucleotide-binding protein GS coupled to beta-adrenergic receptors is involved in transducing signals which inhibit NK cell lysis of tumour cells. CTX and forskolin also diminish the ability of NK cells to bind K562 cells (binding is necessary for lysis). This suggests that the NK-cell receptor(s) for the tumour cell may be altered as a consequence of cAMP-mediated events or by activation of GS.

Adenosine Diphosphate Ribose↗

PubMed1990

Human natural killer cells express Na+ channels. A pharmacologic flow cytometric study.

Voltage-gated excitability of purified human NK cells was studied by using flow cytometry and the voltage-sensitive dye, oxonol. Highly purified human NK cells (CD16 = 95 +/- 1%) from normal volunteers were prepared by using a negative panning technique. The Na(+)-channel agonists batrachotoxin (BTX) (1 to 4 microM) and veratridine (Ver) (100 to 400 microM) depolarized a population of highly purified human NK cells as determined by flow cytometry. BTX and Ver responses were concentration-, time-, temperature-, and Na(+)-dependent. The Na+ channel antagonist tetrodotoxin (1 microM) blocked BTX and Ver responses. Ver (100 microM) produced significant inhibition of cytotoxicity when purified NK cells were incubated with K562 tumor target cells in a 4-h 51Cr release cytotoxicity assay. The effect was blocked by tetrodotoxin. These results strongly suggest presence of functional Na+ channels in NK cells. Activation of voltage-dependent Na+ channels depolarizes cells and reduces their in vitro cytotoxic function.

Batrachotoxins↗

PubMed1990

Depletion of high-energy phosphates in the central nervous system of patients with systemic lupus erythematosus, as determined by phosphorus-31 nuclear magnetic resonance spectroscopy.

Systemic lupus erythematosus (SLE) can produce profound disturbances in the central nervous system, characterized by encephalopathy, focal neurologic deficits, cerebral infarction, psychosis, and seizures. We used 31P nuclear magnetic resonance (NMR) spectroscopy to determine the in vivo levels of high-energy phosphates in the central nervous system of 10 patients with SLE and 10 age-matched normal controls. 31P NMR spectroscopy was performed on a 1.5-Tesla unit equipped with a dual-tuned 1H-31P surface coil and a software-directed DRESS (depth resolved surface coil spectroscopy) pulse sequence. This procedure detected ADP, ATP, sugar phosphates, phosphocreatine (PCr), inorganic phosphate, phosphomonoesters, and phosphodiesters in the brain tissue of all study subjects. Levels of ATP in the deep white matter of 10 SLE patients were significantly decreased compared with the levels in 10 normal controls, as quantitated by the ratio of ATP:ATP + ADP (mean +/- SD 0.81 +/- 0.11 versus 0.91 +/- 0.05; P less than 0.02). In a subgroup of 4 patients, PCr levels were decreased to a greater extent than the ATP levels. NMR spectroscopic alterations were not related to obvious anatomic lesions, as determined by standard cranial proton magnetic resonance imaging. In 4 SLE patients with markedly abnormal 31P NMR spectra, treatment with prednisone (80 mg/day) normalized the levels of ATP and PCr. Restoration of a normal 31P profile was accompanied by an obvious improvement in the patients' mental status and clinical symptoms. 31P NMR spectroscopy is a powerful new technique for monitoring high-energy phosphate metabolism, and may be particularly useful for characterizing central nervous system disease in patients with neuropsychiatric SLE.

Adenosine Diphosphate↗

PubMed1990

Reversal of lovastatin-mediated inhibition of natural killer cell cytotoxicity by interleukin 2.

The activation of human natural killer (NK) cell cytotoxicity by interleukin 2 (IL-2) is well established, although the biochemical mechanisms of this stimulation have not yet been fully delineated. Earlier, we reported that treatment of NK cells with an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase such as compactin or lovastatin significantly abrogates the in vitro killing of a susceptible human erythroleukemic cell line and that this inhibition can be completely reversed by 2 hr of exposure to mevalonate (J. Cell. Physiology 139:550-557, 1989). We report here that 24 hr of treatment with IL-2 also reverses lovastatin inhibition of NK cell function. In addition to natural cytotoxicity, IL-2 also restores chemotactic and antibody dependent cellular cytotoxicity functions to lovastatin-treated cells. IL-2 does not stimulate proliferation of these cells during this time period, nor does it affect the phenotypic composition of the NK cell preparations. Although IL-2 was able to reverse the lovastatin-mediated inhibition of every cell function we examined, it had no effect on the inhibition of cholesterol biosynthesis as measured by [3H]acetate incorporation into non-saponifiable lipids, nor did it stimulate HMG CoA reductase activity. These findings support the hypothesis that there is a non-sterol isoprenoid product which is required for NK cell cytotoxicity and chemotaxis. In addition, the data suggest that IL-2 stimulation of NK cells proceeds by an isoprenoid-independent pathway.

Acetates↗

PubMed1990

Neuropsychiatric lupus erythematosus, cerebral infarctions, and anticardiolipin antibodies.

Anticardiolipin antibody (aCL) has been associated with thromboembolic phenomena, including stroke, in certain patients with systemic lupus erythematosus (SLE); however, the relation between this antibody and the central nervous system manifestations of SLE is unknown. Serum samples and cerebrospinal fluid from five patients with SLE and acute central nervous system manifestations were assayed for the presence of aCL. Anticardiolipin antibody was identified in sera from four of the five patients but in none of the cerebrospinal fluid samples. Nuclear magnetic resonance imaging showed 'infarct-like' lesions in these four patients. This preliminary study suggests that a correlation between serum aCL and cerebral infarcts in central nervous system lupus may potentially exist. From this limited study it seems unlikely that aCL has a direct pathogenic role in the diffuse encephalopathy of acute central nervous system lupus.

Adolescent↗

PubMed1989

Kinetic analysis of effector cell recycling and effector-target binding capacity in a model of cell-mediated cytotoxicity.

A kinetic analysis of cell-mediated cytotoxicity (CMC) at the population level based on theoretical models has been performed. This analysis considers that the binding process and the kinetics of the lytic process occur through different types of conjugates: LTn, i.e., conjugates containing one effector cell and n target cells, and LmT conjugates which contain m effector cells bound to one target cell. This allowed us to provide a quantitative description of the conjugation process, and of the binding capacities of the effector and target cells. Thus, it has been shown that these processes are governed by an equilibrium in which are involved the unbound effector and target cells, and the conjugates formed. This implies that, when the equilibrium concentrations are reached, the total number of conjugates cannot be increased from the unbound effector and target cells. However, it does not mean that the free effector cells are nonbinding, and so, when the conditions of equilibrium are perturbated (as occurs for example in CMC), all effector cells, virgin and those who have already participated in the lytic process, are able to form new conjugates. The existence of this equilibrium has also important consequences when different subpopulations are separated from an effector-target system. Thus, it explains the observation reported in the literature that, although cytometric techniques can be used to detect and count different types of conjugates, the conjugates formed cannot be separated by cell sorting (unless special precautions are taken). Finally, we have found that the number of target cells killed by one effector cell, which has been previously considered as the recycling capacity of an effector population, is in reality the result of two different mechanisms. One of these mechanisms is due to the recycling process, whereas the other (which has the same effect) is due to the multiple killing capacity of the LTn conjugates which kill more than one target cell. The average number of target cells killed per conjugate has been determined, and this allowed us to obtain the relative contributions of these two mechanisms to the total killing capacity of one effector cell. It appears that the recycling capacities of effector cell populations previously determined had been 1- to 3-fold overestimated.

Animals↗

PubMed1989

Quantitation of effector-target affinity in the human NK cell and K562 tumor cell system.

A quantitative procedure to characterize the affinity of human natural killer (NK) cells for K562 tumor is described. Using highly purified (greater than or equal to 98%) NK cells, measurements of the conjugate frequencies permit the determination of the apparent Michaelis constants (KappM) for the conjugation process. Because no intermediate steps for the lytic process are involved the interpretation of the values of KappM is the simplest one that can be achieved. Thus, we found that a plot of KappM against the number of effector cells allows us to determine the dissociation constant, KS, that characterizes the effector-target affinity. KS is independent of the donor cell source and this value was (1.0 +/- 0.1) x 10(5) cell/tube. In contrast, the KappM values vary among donors, and this could be used to compare the relative activity of different donors in relation to their binding capacity.

Adult↗

PubMed1989

Prostaglandins from human T suppressor/cytotoxic cells modulate natural killer antibacterial activity.

We have recently described potent antibacterial activity of purified human NK cells. Here we show that this function is regulated by T cytotoxic/suppressor CD8+ cells. Thus, coculture of NK and CD8+ cells for 3 h or longer times abrogated the expression of the NK antibacterial activity, and of two activation markers IL-2R and transferrin receptor (Tf-R). The suppressive activity was mediated by PGE2 as demonstrated by direct PGE2 determination in CD8+ cell free supernatants, and by inhibition of CD8+ cell suppression with indomethacin or piroxicam in vitro. We also found that resting T cytotoxic/suppressor cells purified by negative selection produce higher amounts of PGE2 than adherent cells like monocytes and macrophages, and that these concentration levels are in the range of concentrations known to suppress a significant number of in vitro immunologic functions.

Antigens, Differentiation, T-Lymphocyte↗

PubMed1989

Model for population distributions of lymphocyte-target cell conjugates.

A quantitative model for the population distributions of the different types of conjugates formed between cytotoxic T lymphocytes and target cells has been developed. The comparison of the theoretical predictions with data of the literature reveals that the transit populations among the different types of conjugates depends on the lymphocyte-to-target ratio, R, and two constants, k and k1. These constants (where k greater than k1) govern, respectively, the transit populations among conjugates of the type LTi (LTn----LTn-1----...LT), and among LjT conjugates (LT----L2T----...----LmT). We have found that high ratios are necessary to obtain conjugates where multiple T lymphocytes are bound to one target cell, and that under these conditions the predominant conjugate, LjT, varies according to j = 1 + k1R. Conversely, for low values of R the predominant population is of the type LTi, where i also shows a linear dependence on R. Our model explains also why the conjugate LT is normally the predominant population under the experimental conditions reported in the literature. A discussion of the influence exerted by the population distributions of lymphocyte-target cell conjugates on the kinetic of the lytic process for these kinds of effector-target systems has also been made.

Immunity, Cellular↗

PubMed1989

Effect of conjugate size on the kinetics of cell-mediated cytotoxicity at the population level.

We developed a model for the kinetics of target cell lysis by cytotoxic T-lymphocytes which accounts for most facts observed at the population level. In contrast to previous models, the following facts: conjugate frequency of cytotoxic T-lymphocytes bound to target cell, dependence of this frequency on the lymphocyte-to-target ratio (R), variation of R with time as target cells are destroyed, and population distributions of the different types of conjugates formed between lymphocytes and target cells, which are involved in the kinetics of these kinds of effector-target systems have been contemplated in the model. The relationship with effector-kinetic analogy models for the lytic process has been discussed. Predictions of the model have been explored and compared with experimental observations about target cell lysis reported in the literature.

Cytotoxicity, Immunologic↗

PubMed1989

The maximum conjugate frequency (alpha max) characterizes killer cell populations.

A quantitative procedure to characterize NK cell populations based on the dependence of the frequency of conjugation (alpha) on the effector-to-target ratio (R) is shown. To this end, a detailed study of the influence exerted by: (a) the value of R; (b) the number of effector and target cells (N, T); and (c) the source (donor) and enrichment of the effector cell population on the frequency of conjugation between NK effector and K562 target cells has been performed. This has demonstrated that for a given value of R large differences in the values of alpha can be obtained for different donors and/or N values. Hence, the usual practice of reporting the frequency of conjugation at a given value of R cannot be used as a valid criterion for comparison, and this could explain the differences in the alpha values reported in the literature for the same effector-target system. Moreover, the frequency of conjugation depends on the enrichment of the effector cell populations, although it has been shown that in all cases a plot of 1/alpha vs. R for N = constant is always linear with intercept 1/alpha max.alpha max represents the maximum frequency of conjugation for an effector-target system and remains constant for all values of R and N, and is also independent on the donor of the cell source. These characteristics make that the values of alpha max can be used as an easy criterion to determine with accuracy conjugate frequencies in an effector-target system, and could also be applied to characterize the activation or inhibition of effector cell populations by monoclonal antibodies or other agents. This criterion was applied to characterize the enrichment of NK cell populations and so, a value of alpha max = 58 +/- 3% has been obtained when highly purified (greater than or equal to 99%) NK effector cells obtained by panning with the monoclonal antibodies Leu-2, Leu-3 and Leu-4 are used. However, the corresponding value for MDC (14% NK cells) was lowered to 26 +/- 1%.

Adult↗

PubMed1989

Experimental and theoretical kinetics study of antibacterial killing mediated by human natural killer cells.

We have recently shown that purified human NK cells, both resting and activated, efficiently kill gram-negative and gram-positive bacteria in vitro. To investigate the mechanism of NK cell-mediated cytotoxicity against Escherichia coli we have developed a mathematical model of the kinetics using the experimental data. The kinetics of killing are characterized by initial target bacterial multiplication, followed by rapid bacterial death. Experiments demonstrates that for each donor there is a threshold number of effector cells necessary to observe a net killing effect. Below the threshold, even use of high effector-to-target ratios lack killing activity and the bacterial growth cannot be stopped. In contrast, if the number of NK cells is larger than the threshold, complete killing is achieved, even at ratios as low as 1/1000. The threshold number varies among donors, ranging between 1200 and 12000 purified NK cells/tube, and provides a quantitative measure of antibacterial activity. Performing the assay at 4 degrees C raised the threshold number required for killing. Experiments performed in Boyden chambers confirm that NK cell-bacteria contact is not necessary for efficient killing, although the kinetics of bacterial lysis is slower. The fit between model and data supports the hypothesis that the bactericidal mechanism is extracellular and is mediated by an anti-microbial factor released from NK cells. Accumulated evidence also indicates that this factor is distinguishable from the mechanisms mediating tumor cell cytotoxicity.

Adult↗