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Biomedical subjects

B S Edwards

Publications and source records attributed to B S Edwards.

At least 19 recordsLinked to original sources
PubMed1996

Enhanced aggregation of human neutrophils by MnCl2 or DTT differentiates the roles of L-selectin and beta 2-integrins.

MnCl2 and dithiothreitol (DTT) enhance the adhesive functions of beta 2 -integrins. We have used these agents and flow cytometry to distinguish the contributions of beta 2-integrins and L-selectin to neutrophil aggregation. Although neither compound induced aggregation, they prolonged N-formyl-methionyl-leucyl-phenylalanine-induced aggregation and produced larger aggregates. Because activated polymorphonuclear granulocytes (PMN) shed L-selectin in the presence of MnCl2, but not DTT, we could evaluate the role of L-selectin in the early and late stages of aggregation. Blocking L-selectin sites with DREG200 Fab and/or beta 2-integrin sites with IB4 Fab indicated that aggregation under all conditions remained beta 2-integrin- and L-selectin-dependent. Disaggregation was integrin-dependent whether L-selectin was present or shed. The disaggregation kinetics suggested that integrin bonds turned over at a slower rate in MnCl2-treated cells. Enhanced aggregation due to DTT and MnCl2 required sustained energy output, suggesting intracellular rather than strictly conformational control. These results provide evidence that PMN aggregation, like leukocyte-endothelial cell adhesion, utilizes L-selectin to form intercellular contacts that are maintained through activated integrins.

Antibody Specificity↗
PubMed1995

Evidence for a dithiol-activated signaling pathway in natural killer cell avidity regulation of leukocyte function antigen-1: structural requirements and relationship to phorbol ester- and CD16-triggered pathways.

Dithiothreitol (DTT) activation of the adhesive function of several different integrins suggests the existence of a common DTT-sensitive integrin regulatory element. Ui11/E3, a natural killer (NK) cell-resistant murine target cell line genetically engineered to constitutively express human intercellular adhesion molecule-1 (ICAM-1; CD54) was used in a flow cytometric experimental model to evaluate DTT effects on the NK cell integrin adhesion molecule, leukocyte function antigen-1 (LFA-1; alpha L beta 2, CD11a/CD18). DTT and several structurally related dithiol compounds elicited a dramatic elevation in conjugate formation that was dependent on target cell ICAM-1 expression, was blocked by LFA-1 alpha L or beta 2 chain-specific antibodies, and occurred in the absence of Ui11/E3 target cell exposure to DTT or quantitative changes in NK cell membrane LFA-1 expression. This avidity modulation of LFA-1 by DTT required actin polymerization, was abrogated by the protein kinase C inhibitor calphostin C, involved activities of calyculin A- and okadaic acid-sensitive serine/threonine protein phosphatases PP-1 and/or PP-2A but not geldanamycin-sensitive tyrosine kinases, and differed with respect to kinetics and enzyme inhibitor sensitivity from LFA-1 activation promoted by cross-linking of NK cell CD16 or phorbol ester treatment. A key structural feature of DTT was the presence of two thiol groups, both reduced but not physically adjacent as in the nonstimulatory dithiol, 2,3-dimercaptopropanol. LFA-1 activation was not because of DTT chelation of Ca2+ or Zn2+. Immunoblotting studies identified multiple NK cell plasma membrane-associated proteins to be reduced by DTT under LFA-1-activating conditions, but similar effects were also promoted by reducing agent treatments that failed to alter adhesive function. Direct chemical modification of LFA-1 seemed an unlikely basis of activation because (1) DTT activated LFA-1 in HSB2 T cells without detectable disulfide reduction in LFA-1 alpha L or beta 2 chains immunoprecipitated from these cells and (2) DTT treatment of NK cells did not hinder binding of KIM127 and KIM185, monoclonal antibodies that recognize epitopes in the potentially DTT-susceptible cysteine-rich domain of the beta 2 chain. Thus, these results extended the range of DTT-activatible integrins to include NK cell LFA-1 and characterized for the first time signaling-associated enzymatic activities involved in DTT activation of NK cell LFA-1. Moreover, they suggested that structural features of DTT, particularly SH group spatial positioning, are important in LFA-activation for reasons other than cation chelation or disulfide reduction.(ABSTRACT TRUNCATED AT 400 WORDS)

Actins↗
PubMed1995

Increase in total plasma homocysteine concentration after cardiac transplantation.

OBJECTIVE: To determine whether plasma homocysteine concentrations are increased in patients after cardiac transplantation. DESIGN: Total plasma homocysteine concentration was measured in 44 consecutive patients before and at 3, 6, and 12 months after orthotopic heart transplantation between June 1, 1988, and Oct. 15, 1992, and the data were analyzed statistically. RESULTS: Mean homocysteine concentrations (normal range, 4 to 17 mumol/L) increased 70% from 12.5 mumol/L before cardiac transplantation to 21.2 mumol/L (P < 0.002) 3 months after transplantation, at which time the concentrations were above normal in 14 of 26 patients (54%). Homocysteine concentrations remained elevated 6 and 12 months after transplantation (20.4 and 22.6 mumol/L, respectively) but did not increase further. Mean concentrations of plasma folic acid and vitamin B12, cofactors in homocysteine metabolism, decreased 20% and 49%, respectively, within 3 months after transplantation (11.6 to 9.3 micrograms/L [P = 0.04] and 584 to 295 ng/L [P = 0.01]). The mean glomerular filtration rate decreased 25% during this same interval (81 to 61 mL/min; P = 0.0001). Linear regression analysis revealed an association between the increase in homocysteine concentration and the folic acid concentration that approached statistical significance (P = 0.07); we found no statistically significant correlates of the increase in homocysteine concentration. CONCLUSION: The homocysteine concentration increases in most patients within 3 months after cardiac transplantation to levels previously associated with premature atherosclerotic coronary artery disease, and it remains increased for at least 1 year. Further investigation into the mechanism for the increase in homocysteine concentration and the relationship between homocysteine and coronary artery disease after transplantation is warranted.

Adolescent↗
PubMed1994

Diagnosis of coronary artery atheroembolism by right ventricular endomyocardial biopsy.

A case of coronary artery atheroembolism in a 54-year-old man, presenting as worsening congestive heart failure 2 months after mitral valve repair, left ventricular aneurysmectomy, and coronary artery bypass grafting, is reported. The diagnosis was made by right ventricular endomyocardial biopsy. The authors believe this to be the first such account in the literature.

Arterioles↗
PubMed1993

Calcium mobilization-associated and independent cytosolic acidification elicited in tandem with Na+/H+ exchanger activation in target cell-adherent human NK cells.

Flow cytometry was used to identify mechanisms by which human NK cells regulate intracellular pH (pHi) and to investigate the relationship between NK cell pHi and cytolytic function. Temporally resolved determinations of pHi were simultaneously made in NK cells that formed conjugates with target cells (NKC) and unconjugated NK cells (NKU) on the basis of the red/orange fluorescence emission ratio of the pH indicator seminapthylrhodafluor-1. Two pHi regulatory mechanisms were identified in NK cells: 1) a HCO3-/Cl- antiport that promoted pHi changes in response to variation of extracellular HCO3- and Cl- but not Na+ ion concentrations, was sensitive to stilbene derivatives 4,4'-diisothiocyanatostilbene sulfonic acid and 4-acetamido-4'-isothyocyanotostilbene-2-2'-disulfonic acid, and exhibited similar activity in NKC and NKU, and 2) a Na+/H+ exchanger that promoted pHi changes in response to extracellular Na+ ion concentration changes and was sensitive to dimethylamiloride (DMA), permeable to Na+ and Li+ but not K+ or N-methyl-D-glucamine, and quiescent in NKU but activated in target cell-adherent NKC. When Na+/H+ exchange was blocked with 10 microM DMA, the pHi of NKC bound to NK-sensitive K562 target cells progressively decreased for 3 to 4 min, then stabilized at 0.1 to 0.15 pH units below the pHi of NKU. A significant temporal decline in NKC pHi also occurred in the nominal absence of extracellular Ca2+ (0.07 +/- 0.02 pH units) and when NKC formed conjugates with NK-resistant B lymphoblastoid target cells that failed to mobilize NK cell Ca2+ (0.07 +/- 0.01 pH units) (mean +/- SD). However, the magnitude of the NKC cytosolic acidification response was consistently reduced (42 +/- 4 and 44 +/- 6%, respectively) under these Ca2+ flux response-limiting conditions. Thus, adhesion to target cells triggered two pHi-related responses in NK cells: 1) a decline in pHi which exhibited both Ca2+ mobilization-dependent and -independent components, and 2) Na+/H+ exchanger activation by which acid production was neutralized. Manipulations of HCO3- and DMA that clamped NKC pHi at values ranging from 6.8 to 7.2 failed to significantly influence NK cell cytolytic function. By contrast, isosmotic replacement of extracellular Na+ with NMDG resulted in a 57 +/- 22% inhibition of NK cell-mediated cytolysis (n = 8, p < 0.01). NKC pHi declined to 6.8 to 6.9 under these conditions, but this was not the apparent basis of impaired cytolysis because sustained elevation of NKC pHi by addition of dimethylamine failed to significantly reverse inhibition.(ABSTRACT TRUNCATED AT 400 WORDS)

Amiloride↗
PubMed1993

The synergistic effects of cyclosporine and endothelin--demonstration of an important cardiodepressor action.

Cyclosporine represents the foundation for current immunosuppressive therapy following solid organ transplantation. CsA use is associated with renal insufficiency and systemic hypertension. We hypothesized that CsA would enhance the vascular actions of endothelin (ET). Three groups of anesthesized dogs (n = 15) were studied. Group 1 received CsA alone (1 mg/kg), group 2 received ET alone (1 ng/kg/min), and group 3 received combined CsA (1 mg/kg) and ET (1 ng/kg/min). The hemodynamic and renal effects were evaluated after 30 min. Combined treatment resulted in a profound reduction in mean arterial pressure (-62 +/- 14 mmHg (P < .05) and cardiac output (-2.2 +/- 0.4.1/min (P < .05). The reduction in mean arterial pressure and cardiac output were significantly greater than that observed with CsA or ET alone. Systemic vascular resistance was not significantly changed. Combined CsA and ET resulted in a significant reduction in renal blood flow (195 +/- 18 to 101 +/- 11 ml/mm P < .05) but without evidence of active renal vasoconstriction. The decline in GFR (31.8 +/- 5.6 ml/min to being unmeasurable) was of greater magnitude than the change in renal blood flow, suggesting enhanced afferent anteriolar vasoconstriction or an alteration in the ultrafiltration coefficient. These studies demonstrate an important and synergistic cardiodepressor effect when CsA and ET are combined.

Animals↗