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F H Valone

Publications and source records attributed to F H Valone.

70 records · Page 4Linked to original sources
PubMed1982

Specific binding of phospholipid platelet-activating factor by human platelets.

The binding of the phospholipid platelet-activating factor 1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphorylcholine (AGEPC) to washed human platelets was more than 80% complete within 2 min, which coincided with the time of initiation of platelet aggregation by AGEPC. Scatchard plot analysis of the binding of [3H]AGEPC to platelets without and with an excess of unlabeled AGEPC revealed two distinct types of binding sites. One platelet site for AGEPC exhibited a high affinity (KD = 37 +/- 13 nM, mean +/- SD), was saturable, and had a low maximal capacity of 1399 +/- 498 (mean +/- SD) molecules of AGEPC/platelet. The other platelet site demonstrated a nearly infinite binding capacity, consistent with nonreceptor uptake of AGEPC into cellular structures. The specificity of the high-affinity binding site for AGEPC was assessed by comparing the capacity of several analogues of AGEPC to inhibit the binding of [3H]AGEPC to platelets and to induce platelet aggregation. An ether linkage in position 1, a short-chain fatty acid in position 2, and a choline moiety in the polar head group proved to be critical both for the binding of [3H]AGEPC to platelets and for the initiation of platelet aggregation. Exposure of platelets to AGEPC for 5 min at 37 degrees C functionally deactivated the exposed platelets to subsequent stimulation by AGEPC, as assessed by diminished aggregation, and concomitantly reduced the specific binding of [3H]AGEPC. Evaluation of the time course of the events of deactivation revealed the loss of an aggregation response to AGEPC after 90 sec at 37 degrees C, despite the retention of up to 50% of the specific binding sites for AGEPC.

Blood Platelets↗
PubMed1980

Structural requirements for the activity of an immunologically generated lipid chemotactic factor.

The predominant lipid chemotactic factor (LCFR) generated by IgGa-dependent immunological challenge of the rat peritoneal cavity was resolved from other lipid mediators released simultaneously into the peritoneal cavity and from previously described lipid chemotactic factors by sequential chromatography on Amberlite XAD-8, DE-52, silicic acid, and silica gel H plates, and by Zorbax C-18 reverse phase high pressure liquid chromatography. The incubation of purified rat peritoneal mononuclear leucocytes, but not mast cells, with calcium ionophore A23187 in vitro resulted in the generation of LCFR activity which was chromatographically identical to the LCFR released in vivo. That indomethacin inhibited the appearance of LCFR both in vivo and in vitro indicated a dependence on the cyclo-oxygenation of arachidonic acid. Because of the limited quantities of highly purified LCFR, the critical determinants of human neutrophil chemotactic activity were studied by examining the functional effects of chemical modification of specific substituents. The chemotactic activity of LCFR was diminished significantly by acetylation with acetic anhydride in pyridine or methylation with ethereal diazomethane, but was not influenced by 0.1 M periodate or acid or base hydrolysis, suggesting that LCFR is a complex fatty acid containing a hydroxyl or amino group. The addition of acetylated LCFR to the stimulus compartment at a 0.3-0.5 molar ratio with native LCFR diminished the neutrophil chemotactic response by 50%, without affecting a comparable response to f-Met-Leu-Ala-Phe. Thus LCFR is a unique lipid chemotactic factor which is distinct from other lipid mediators and accounts for the bulk of the PMN leucocyte chemotactic activity released by immunological challenge of the rat peritoneal cavity.

Animals↗
PubMed1979

Specific inhibition of the polymorphonuclear leukocyte chemotactic response to hydroxy-fatty acid metabolites of arachidonic acid by methyl ester derivatives.

The human polymorphonuclear (PMN) leukocyte chemotactic activity of the hydroxy-fatty acid metabolites of arachidonic acid, 12-l-hydroxy-5,8,10-heptadecatrienoic acid (HHT) and 12-l-hydroxy-5,8,10,14-eicosatetraenoic acid (HETE), is eliminated by methylation. Both methyl esters are specific competitive inhibitors of the PMN leukotactic responses to the parent stimuli, and exert no effect on the responses to formyl-methionyl peptides or chemotactic fragments of the fifth component of complement. 50% inhibition of the in vitro chemotactic responses of PMN leukocytes to HETE and HHT was achieved by an equimolar concentration of the corresponding methyl esters, whereas reciprocal cross-inhibition was observed at molar ratios of HETE methyl ester to HHT and HHT methyl ester to HETE which reflected the three- to fivefold greater chemotactic potency of HETE relative to HHT. Methyl esters of structurally related, but nonchemotactic, fatty acids did not competitively inhibit the chemotaxis elicited by HETE or HHT. The intraperitoneal injection of HETE in guinea pigs evoked an eosinophil response at 30 min and a neutrophil response at 5 h, which were prevented by a one-to twofold molar ratio of HETE methyl ester. The competitive inhibition of the in vitro chemotactic activity and the in vivo leukotactic effect of the unsaturated hydroxy-fatty acids by homologous methyl ester derivatives suggests that the cellular component of natural inflammatory reactions may be susceptible to specific regulation by receptor-directed modulation of the activity of the predominant chemotactic principles.

Arachidonic Acids↗
PubMed1979

The immunological generation of a platelet-activating factor and a platet-lytic factor in the rat.

Antigen challenge of the rat peritoneal cavity which had been prepared with IgGa-rich antiserum generated activities which released [14C]-serotonin from pre-labelled human platelets. After adsorption of these activities onto Amberlite XAD-8 and elution in 80% ethanol, two factors of differing polarity were resolved by chromatography on diethylaminoethyl cellulose in organic solvents. The activity eluting in the 7:1 chloroform:methanol solvent contained a platelet-lytic factor (PLF) assessed by the parallel release of lactic acid dehydrogenase and [14C]-serotonin; the cytotoxicity of this fraction was confirmed by phase-contrast microscopy examination which demonstrated fragmentation of the exposed platelets. The activity eluting in the 1:1 methanol: aqueous 1.0 M ammonium carbonate solvent was a platelet-activating factor (PAF) as defined by release of [14C]-serotonin without lactic acid dehydrogenase. Both the lytic and the activating principles were separable from slow reacting substance of anaphylaxis and polymorphonuclear leucocyte chemotactic activity, and each presented a single activity peak of differing mobility when chromatographed on silica gel H plates. Human eosinophil phospholipase D inactivated the lytic factor by more than 85% in 2 h at 37 degrees without affecting the activity of the activating factor. The release of [14C]-serotonin induced by the PAF was not affected by the absence of calcium from the medium or by elevations in the platelet concentrations of cyclic AMP or cyclic GMP that resulted from pre-incubation of platelets with prostaglandin D2 or sodium ascorbate, respectively.

Animals↗
PubMed1975

The release of four mediators of immediate hypersensitivity from human leukemic basophils.

The availability of a patient with basophilic leukemia manifesting 75 to 90% mature basophils permitted the use of a cell concentration sufficient to generate and release mediators upon interaction with a calcium ionophore in quantities adequate for their physiocochemical characterization. The mediators were defined in terms of their physicochemical characteristics: slow reacting substance of anaphylaxis (SRS-A) by purification through silicic acid chromatography and inactivation by arylsulfatase; eosinophil chemotactic factor of anaphylaxis (ECF-A) by its gel filtration through Sephadex G-25 and inactivation by subtilisin and not trypsin; and platelet-activating factor (PAF) by its inherent binding to albumin. Both ECF-A and histamine were present in their preformed state, and for histamine it was possible to establish that the concentration per cell was comparable to that of normal human basophils. Dibutyryl cyclic AMP suppressed release of histamine and SRS-A, indicating that their availability was under a control similar to that observed with normal cells subjected to immunologic activation. The demonstration that a suspension of leukemic human basophils contained the preformed mediators, histamine and ECF-A, and generated SRS-A and PAF for release along with histamine and ECF-A, after activation with a calcium ionophore, establishes that a single cell type can serve as a source of the four recognized mediators of immediate-type hypersensitivity.

Aged↗
PubMed1974

Modulation of the random migration of human platelets.

Random migration of human platelets has been recognized as a parameter of platelet function which can be assessed in a reproducible manner by modification of the Boyden micropore filter technique for evaluating this function in other cells (Boyden, S. 1962. J. Exp. Med. 115: 453-466). Because platelets are extremely susceptible to aggregation, the conditions for collecting and isolating platelets and the migration buffer (Ca(++) and Mg(++)-free phosphate buffered saline, pH 6.8, with glucose and gelatin) were selected to minimize such a possibility. The random movement of platelets into the micropore filter was maximal at 30-37 degrees C and was contingent upon the metabolic integrity of the cell; thus, it can be attributed to active spontaneous migration. While the initiating and enhancing effects of epinephrine on the platelet aggregation-release reaction are mediated by an alpha-adrenergic receptor, the inhibition of random migration involved a beta-receptor. Equimolar propranolol but not phentolamine prevented epinephrine inhibition of random migration, and isoproterenol had activity comparable to epinephrine while phenylephrine was inactive. The capacity of the cholinomimetic agent, carbachol, to increase platelet migration is reminiscent of the recent findings in several cell systems in which beta-adrenergic and cholinergic stimuli have opposite effects. The prostaglandins E1 and E2 augmented spontaneous migration in contrast to their well established inhibitory action on platelet aggregation at the concentrations employed. The suppression by indomethacin of prostaglandin enhancement and of spontaneous migration implies a requirement for the prostaglandin biosynthetic pathway during the migration process. Thus, the spontaneous migration of human platelets, an additional parameter of platelet function for in vitro investigations, disclosed not only a beta-adrenergic receptor for epinephrine, but also a capacity for cholinergic augmentation and an apparent requirement for prostaglandin biosynthesis.

Blood Platelets↗
PubMedDate not supplied

Dendritic cell-based treatment of cancer: closing in on a cellular therapy.

PURPOSE: Dendritic cells are the most potent antigen-presenting cells and are critical to initiation of immune responses. Dendritic cells loaded ex vivo with tumor-associated antigen are being administered to cancer patients in an effort to jump-start a potent, cell-mediated anticancer immune response resulting in tumor shrinkage and clinical benefit. PATIENTS AND METHODS: Dendreon Corporation has designed three therapeutic vaccines using blood-derived dendritic cells loaded ex vivo with antigen: Provenge for prostate cancer; Mylovenge for multiple myeloma and other B-cell malignancies; and APC8024 for cancers expressing the HER-2/neu proto-oncogene. RESULTS: Preclinical studies demonstrated that blood dendritic cells matured spontaneously in short-term culture without growth factors, and that fusion of antigens with granulocyte-macrophage colony-stimulating factor enhances antigen uptake and presentation by blood dendritic cells. Phase I/II trials suggest that these dendritic cell-based vaccines are safe and well tolerated. Provenge has demonstrated antitumor activity in hormone-refractory prostate cancer; approximately 20% of patients experienced decreased prostate-specific antigen (i.e., PSA) levels and a similar percentage experienced disease stabilization. Double-blind, placebo-controlled, randomized trials in metastatic, asymptomatic hormone-refractory prostate cancer have been initiated. Phase II data on Mylovenge are similarly encouraging, and expanded phase II testing is ongoing in anticipation of opening phase III trials in 2002. APC8024 is in early clinical development and has shown significant capacity to elicit antigen-specific immune responses. CONCLUSION: Antigen delivery by ex vivo antigen-loaded dendritic cells may be an effective approach to cancer immunotherapy.

Cancer Vaccines↗
PubMedDate not supplied

Soluble normal and mutated DNA sequences from single-copy genes in human blood.

Healthy individuals have soluble (extracellular) DNA in their blood, and increased amounts are present in cancer patients. Here we report the detection of specific sequences of the cystic fibrosis and K-ras genes in plasma DNA from normal donors by amplification with the polymerase chain reaction. In addition, mutated K-ras sequences are identified by polymerase chain reaction utilizing allele-specific primers in the plasma or serum from three patients with pancreatic carcinoma that contain mutated K-ras genes. The mutations are confirmed by direct sequencing. These results indicate that sequences of single-copy genes can be identified in normal plasma and that the sequences of mutated oncogenes can be detected and identified with allele-specific amplification by polymerase chain reaction in plasma or serum from patients with malignant tumors containing identical mutated genes. Mutated oncogenes in plasma and serum may represent tumor markers that could be useful for diagnosis, determining response to treatment, and predicting prognosis.

Aged↗