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At least 883 records · Page 49Linked to original sources
PubMed2004

Spectroscopic investigation of the aggregation state of amphotericin B during loading, freeze-drying, and reconstitution of polymeric micelles.

PURPOSE: To investigate the relative aggregation state of amphotericin B (AmB) during loading and reconstitution of polymeric micelles. METHODS: Hexanoate and stearate derivatives of PEO-b-p (L-Asp) were prepared. The polymers and AmB were dissolved in methanol (MeOH). Milli-Q water was then added slowly, and the MeOH was removed via rotary evaporation. The solutions were freeze-dried in the presence of trehalose. During micelle preparation, the aggregation state of AmB was assessed using absorption spectroscopy. Upon reconstitution, the samples were analyzed using vapor-pressure osmometry, size-exclusion chromatography (SEC), and absorption spectroscopy. The absorption spectrum of AmB in the presence of the block copolymers was compared to that of AmB alone under the same conditions. RESULTS: AmB was loaded into micelles prepared from acyl derivatives of PEO-b-p (L-Asp). Absorption spectroscopy indicated that the aggregation state was preserved during the loading process. AmB exists in a self-aggregated state in polymeric micelles containing hexanoate ester cores and in a relatively monomeric state in polymeric micelles containing stearate ester cores. Vapor-pressure osmometry confirmed the isotonicity of the formulations, while SEC indicated that the micelles were approximately 10(6) g/mol. CONCLUSIONS: Depending on the polymer structure and assembly conditions, it is possible to encapsulate AmB in a relatively nonaggregated or aggregated state in micelles prepared from acyl derivatives of PEO-b-p (L-Asp). In polymeric micelles containing stearate side chains, AmB was loaded in a nearly monomeric state, possibly due to interaction with the stearate side chains. The final aggregation state of the drug is preserved during lyophilization and reconstitution of polymeric micelles prepared by a novel solvent evaporation procedure.

Amphotericin B↗
PubMed1992

Effects of the neuronal phosphoprotein synapsin I on actin polymerization. II. Analytical interpretation of kinetic curves.

The general features of the kinetics of actin polymerization are investigated by mathematical models, with the aim of identifying the kinetically relevant parameters in the process and detecting and interpreting the alterations occurring in actin polymerization under various experimental conditions. Polymerization curves, obtained by following the increase in fluorescence of actin derivatized with N-(1-pyrenyl) iodoacetamide, are fitted using analytical equations derived from biochemical models of the actin polymerization process. Particular attention is given to the evaluation of the effects of the neuronal phosphoprotein synapsin I. The models obtained under various ionic conditions reveal that synapsin I interacts with actin in a very complex fashion, sharing some of the properties of classical nucleating proteins but displaying also actions not described previously for other actin-binding proteins. Synapsin I appears to bind G-actin with a very high stoichiometry (1:2-4), and the complex behaves as an F-actin nucleus, producing actin filaments under conditions where spontaneous polymerization is negligible. These actions of synapsin I are markedly affected by site-specific phosphorylation of the protein. An original transformation of the fluorescence data, which estimates the disappearance rate of actin monomer toward the critical concentration, is presented and shown to be of general usefulness for the study of actin-binding proteins.

Actins↗
PubMed1992

Interaction between complementary polymerization sites in the structural D and E domains of human fibrin.

Plasmic degradation products of human fibrin, fragments DD, D, and E, bind to fibrin. It has been inferred from this observation that the binding occurs by attraction of complementary sites located in the NH2- and COOH-terminal domains of the fibrin molecule. The interaction between fragments D1 and E1 has been investigated in this work since it represents the first step in the process of fibrin clot formation. Fragment D1, that was initially as active as fragment DD, lost most of its anticoagulant activity after purification by cation-exchange chromatography. The lability of fragment D1 function explained the previous unsuccessful attempts to form a complex between fragments D1 and E1. The loss of fragment D1 anticoagulant activity was not associated with the cleavage of the gamma 63-85 chain segment, since fragments D1A and D1 identically inhibited the fibrin monomer polymerization rate. In order to demonstrate the formation of a complex between fragments D1 and E1, three lines of experiments were advanced. First, the anticoagulant activity of fragment D1 was neutralized by fragment E1 in a dose-dependent manner, demonstrating that the association between these fragments involved polymerization sites. Second, two products, D1.E1 and D1.E1.D1, were stabilized in a reaction with bifunctional cross-linking reagents, proving the formation of D.E complexes in aqueous solution. Third, immobilized fragment D1 bound fragments E1 and E2, but not fragment E3, showing that fragments E1 and E2 attached via a polymerization site to the complementary one in fragment D1, since this association was disrupted by fibrin polymerization inhibitory peptide GPRP. These results provided direct evidence for specific binding between the structural D and E domains of fibrin mediated through complementary polymerization sites. Thus, the initial formation of fibrin clot fibers appears to be driven by specific association of these sites.

Amino Acid Sequence↗
PubMed2005

[Effect of polymeric scaffolds on attachment and growth of bone marrow mesenchymal stem cells].

To investigate the effect of three kinds of polymeric scaffolds on attachment, proliferation and differentiation of bone marrow mesenchymal stem cells, the cells were different polymeric scaffolds of PLA-PEG, PLA, PLGA, respectively. The proliferation of cell was evaluated by cell count; the attachment and morphology of BMSCs were observed by SEM; and differentiation was detected by alkaline phosphatase activity, fluorescence, and RT-PCR methods. Results showed that the cells in PLGA group spread better among BMSCs adhered to the three polymeric scaffolds. The activity of ALP was detected after 3 days culture in these three groups. There were no significant differences between PLA-PEG and PLGA groups, but the activity of ALP was higher than PLA group. The gene expressions of osteocalicin and collagen I were also observed in the early culture time. Calcium nodes formation in these polymeric scaffolds were detected. BMSC spreading first, then overlapping growth and secretion of matrix around the bottom and surface of scaffolds were observed through SEM. In summary, PLA-PEG and PLGA are better polymeric scaffolds for the bone tissue engineering, compared with PLA.

Bone Marrow Cells↗
PubMed2006

A review of polymerization shrinkage stress: current techniques for posterior direct resin restorations.

In general excellent results cannot be guaranteed when using resin-based composites for posterior restorations. This is due to polymerization shrinkage which can still be regarded as the primary negative characteristic of composite resins. A review of available literature regarding the polymerization process, its flaws, and suggested strategies to avoid shrinkage stress was conducted. Several factors responsible for the polymerization process may negatively affect the integrity of the tooth-restoration complex. There is no straightforward way of handling adhesive restorative materials that can guarantee the reliability of a restoration. At present, the practitioner has to coexist with the problem of polymerization shrinkage and destructive shrinkage stress. However, evolving improvements associated with resin-based composite materials, dental adhesives, filling, and light curing techniques have improved the predictability of such restorations. This critical review paper is meant to be a useful contribution to the recognition and understanding of problems related to polymerization shrinkage and to provide clinicians with the opportunity to improve the quality of composite resin restorations.

Bicuspid↗
PubMed1977

Comparison of polymerization of ancrod and thrombin fibrin monomers.

The polymerization of thrombin and ancrod fibrin monomers was studied with a standardized technique that evaluated turbidity changes and protein incorporation into the clot. Ancrod fibrin monomers were found to polymerize more slowly and form less turbid clots (at identical protein concentrations). Changes in ionic strength and pH influences ancrod fibrin monomer polymerization to a greater extent than thrombin fibrin monomer polymerization. Benzyltriethylammonium chloride was shown to be a potent inhibitor of fibrin monomer polymerization, with a greater inhibitory effect on ancrod fibrin monomers than on thrombin fibrin monomers. The differences between ancrod and thrombin fibrin may play a role in the infrequent thrombotic complications reported with ancrod therapy.

Ancrod↗
PubMedDate not supplied

Comparison of microwave-polymerized denture base resins.

Three denture base resins, two designed for microwave polymerization and one for host-water-bath-processing, were compared. Results indicated that all four tested thicknesses (3, 6, 11.6, and 17.7 mm) of the water-bath-polymerized samples and one of the microwave-polymerized resins were porosity-free. When the water-bath-polymerized material was microwave processed, porosity was found when resin thickness exceeded 3 mm. When one resin designed for microwave polymerization was irradiated using the high-wattage (513 W), shorter cycle (4 minutes 52 seconds), porosity also occurred when the thickness exceeded 3 mm. Porosity did not occur until there was 9 mm of thickness when the lower-wattage (75.9 W), longer cycle (15 minutes 26 seconds) was used. No significant differences in transverse strength or hardness were noted between the materials.

Denture Bases↗
PubMed1990

Anion-linked polymerization of the tetrameric hemoglobin from Scapharca inaequivalvis. Characterization and functional relevance.

The anion-linked polymerization of the tetrameric hemoglobin from Scapharca inaequivalvis has been characterized by means of sedimentation velocity experiments in terms of its dependence on the binding of other protein ligands, oxygen, and protons. The linkage with oxygen manifests itself at any given anion concentration in the markedly different sedimentation behavior of the oxygenated and deoxygenated protein; whereas the former sediments always as a single peak (congruent to 4.3 S), the latter exhibits bimodal Schlieren patterns with a fast peak that attains congruent to 10 S. A comparison of experimental and computer-simulated (Cox, D. J. (1971) Arch. Biochem. Biophys. 146, 181-195) boundaries shows that the behavior of oxyhemoglobin can be represented by a rapidly reversible dimerization of the native 4.3 S molecule, whereas the behavior of the deoxygenated protein can be described adequately in terms of the polymerization of the native structure into tetramers and octamers. The interplay between the binding of protons and anions is brought out by the different dependence of polymer formation on anion concentration at different pH values. In the case of chloride, polymerization goes through a maximum at around 20-50 mM Cl- at pH 6.3 but decreases monotonically above 5 mM at pH 5.5. On the basis of these data and of the effect of other anions such as phosphate and perchlorate, a tentative picture of the high affinity anion-binding sites has been proposed. From a functional point of view, the hemoglobin polymers are characterized by a lower oxygen affinity and a higher cooperativity than the tetrameric structure; hence, polymerization results in a shift of the lower asymptote of the Hill plots while the upper asymptote is unaltered. The effect of polymerization on oxygen binding has been analyzed in terms of the polysteric linkage scheme (Colosimo, A., Brunori, M., and Wyman, J. (1974) Biophys. Chem. 2, 338-343). The data obtained at pH 6.3 as a function of chloride concentration could be fitted satisfactorily by taking the self-association behavior of the protein into account.

Animals↗
PubMed1990

pp60v-src association with the cytoskeleton induces actin reorganization without affecting polymerization status.

The mechanism by which Rous sarcoma virus (RSV) induces a reorganization of actin and its associated proteins and a reduction in microfilament bundles is at present poorly understood. To examine the relationship between the organization of the microfilament system and the polymerization state of actin after transformation, we have investigated these changes in a Rat-1 cell line transformed by LA29, a temperature-sensitive (ts) mutant of RSV. Parallel immunofluorescence and biochemical analysis demonstrated that LA29 pp60v-src was ts for tyrosine kinase activity and cytoskeletal association. Changes in the distribution and organization of actin, alpha-actinin and vinculin were dependent on the association of a kinase-active pp60v-src molecule with the detergent-insoluble cytoskeleton. Whilst there was a transformation-dependent loss of microfilament bundles, biochemical quantitation demonstrated that the polymerization state of the actin in both detergent-soluble and insoluble fractions of these cells grown at temperatures either permissive or restrictive for transformation was quantitatively unchanged. These results indicate that the loss of microfilament bundles after transformation is not due to a net depolymerization of filamentous actin but rather to a reorganization of polymeric actin from microfilament bundles and stress fibers to other polymeric forms within the cell. The polymeric nature of the actin in these cells was confirmed by electron microscopy of cytoskeletons and substrate-adherent membranes.

Actin Cytoskeleton↗
PubMed1990

The polymerization and thrombin-binding properties of des-(B beta 1-42)-fibrin.

Multiple factors affect the thrombin-catalyzed conversion of fibrinogen to fibrin, including: fibrinopeptide (FPA and FPB) release leading to exposure of two types of polymerization domains ("A" and "B," respectively) in the central portion of the molecule, and exposure of a noncatalytic "secondary" thrombin-binding site in fibrin. Fibrinogen containing the FPA sequence but lacking the B beta 1-42 sequence ("des-(B beta 1-42)-fibrinogen"), was compared to native fibrinogen (containing both FPA and FPB) to investigate the role played by B beta 1-42 in the polymerization of alpha-fibrin (i.e. fibrin lacking FPA), to compare reptilase and thrombin cleavage of FPA from fibrinogen, and to explore the location and function of the secondary thrombin-binding site. Electron microscopy of evolving polymer structures (mu, 0.14; pH 7.4) plus turbidity measurements, showed that early thin fibril formation as well as subsequent lateral fibril associations were impaired in des-(B beta 1-42)-alpha-fibrin, thus indicating that the B beta 1-42 sequence contributes to the A polymerization site. Reptilase-activated des-(B beta 1-42)-alpha-fibrin polymerized even more slowly than thrombin-activated des-(B beta 1-42)-alpha-fibrin, differences that disappeared when repolymerization of preformed fibrin monomers was carried out. Since existing data indicate that thrombin releases FPA in a concerted manner, resulting in relatively rapid evolution of fully functional divalent alpha-fibrin monomers, it can be inferred that delayed fibrin assembly of reptilase fibrin is due to slower formation of divalent alpha-fibrin monomers. Thrombin-activated des-(B beta 1-42)-alpha-fibrin polymerized more rapidly at low ionic strength (mu, 0.04) than did native alpha,beta-fibrin, a reversal of their behavior at physiological ionic strength (mu, 0.14). Concomitant measurement of FPA release revealed modest slowing of release at low ionic strength from des-(B beta 1-42)-fibrinogen (t1/2, 36.5 versus 21.5 min) and marked slowing from native fibrinogen (t1/2, 138 versus 22.2 min). This behavior correlated with increased thrombin binding to native alpha,beta-fibrin at low ionic strength, coupled with weak thrombin binding to des-(B beta 1-42)-alpha-fibrin, and indicates that secondary thrombin binding plays an important role in regulating thrombin diffusion and catalytic activity. Des-(B beta 1-42)-fibrinogen lacks or has a markedly defective secondary thrombin-binding site, from which we conclude that the B beta 15-42 sequence in fibrin plays a major role in forming or providing this site.

Batroxobin↗
PubMed1990

The cDNA sequences encoding two components of the polymeric fraction of the intracellular hemoglobin of Glycera dibranchiata.

The intracellular hemoglobin of the polychaete Glycera dibranchiata consists of several components, some of which self-associate into a "polymeric" fraction. The cDNA library constructed from the poly(A+) mRNA of Glycera erythrocytes (Simons, P. C., and Satterlee, J. D. (1989) Biochemistry 28, 8525-8530) was screened with two oligodeoxynucleotide probes corresponding to the amino acid sequences MEEKVP and AMNSKV. Each of the two probes identified a full-length positive insert; these were sequenced using the dideoxynucleotide chain termination method. One clone was 630 bases long and contained 36 bases of 5'-untranslated RNA, a reading frame of 441 bases coding for the 147 amino acids of globin P2 including the residues MEEKVP, and a 3'-untranslated region of 153 bases. The other clone was 540 bases long and contained 24 bases of 5'-untranslated RNA, an open reading frame of 441 bases coding for globin P3 including the residues AMNSKV, and a 3'-untranslated region of 75 bases. The inferred amino acid sequences of the two globins were in agreement with the partial amino acid sequences obtained by chemical methods. The P2 and P3 globin sequences, together with the previously determined P1 sequence of a complete insert and partial sequences P4, P5, and P6 obtained from partial inserts (Zafar, R. S., Chow, L. H., Stern, M. S., Vinogradov, S. N., and Walz, D. A. (1990) Biochim. Biophys. Acta, in press) suggest that there are at least six components in the polymeric fraction of Glycera hemoglobin, which is in agreement with the results of polyacrylamide gel electrophoresis in Tris/glycine buffer, pH 8.3, 6 M urea. Nothern and dot blot analyses of Glycera erythrocyte poly(A+) mRNA using the foregoing two cDNA probes clearly demonstrated the presence of mature messages encoding both types of globins. Comparison of the polymeric sequences P1, P2, and P3 with the "monomeric" globins M-II and M-IV using the alignment and templates of Bashford et al. (Bashford, D., Chothia, C., and Lesk, A. M. (1987) J. Mol. Biol. 196, 199-216) showed that all five globins have identical residues at 39 positions. At 44 positions, the three polymeric globins share identical residues that differ from the identical residues at the corresponding locations in the monomeric sequences M-II and M-IV including position E7, where the latter have leucine instead of the distal histidine. At 15 positions, there occurs an alteration from polar to nonpolar or from a small nonpolar to a larger nonpolar residue in going from the monomeric to the polymeric globins.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1989

Microleakage with Gluma: effects of unfilled resin polymerization and storage time.

An earlier study showed that the Gluma Bonding System permitted more microleakage than other dentin bonding agents. In that study, the unfilled resin was not polymerized prior to placement of the composite resin, as per manufacturer's instructions. The unfilled resin was cured in the other test groups. To evaluate the effect of unfilled resin polymerization on microleakage, Class V cavity preparations were made in sound extracted teeth. Composite resin restorations were placed using the Gluma Bonding System and a microfilled composite resin. In some samples, the unfilled resin was cured prior to placement of the composite. In others, the unfilled resin and composite were polymerized simultaneously. The samples were stored for either 24 hours or 30 days, then thermocycled. Microleakage was evaluated with a silver nitrate staining method. Specimens in which the unfilled resin had not been cured separately and which had been stored for 24 hours had the most leakage. Significantly less microleakage occurred when the unfilled resin was polymerized separately and/or when storage time was 30 days. To reduce microleakage with the Gluma Bonding System, the authors recommend polymerization of the unfilled resin before placement of the composite.

Aldehydes↗
PubMed1978

Polymerization of actin. V. A new organelle, the actomere, that initates the assembly of actin filaments in Thyone sperm.

Between the acrosomal vacuole and the nucleus is a cup of amorphous material (profilactin) which is transformed into filaments during the acrosomal reaction. In the center of this cup in untreated Thyone sperm is a dense material which I refer to as the actomere; it is composed of 20-25 filaments embedded in a dense matrix. To visualize the substructure of the actomere, the profilactin around it must be removed. This is achieved either by demembranating the sperm with Triton X-100 and then raising the pH to 8.0, or by adding inophores to intact sperm at pH 8.0. Under these conditions, the actomere remains as a unit while the rest of the profilactin is solubilized or polymerized. When demembranated sperm are incubated under conditions in which the actin should polymerize, filaments grow from the end of the actomere: the actomere thus appears to behave as a nucleating body. This observation is strengthened by experiments in which untreated sperm are incubated in seawater or isotonic NaCl at pH 7.0 and the ionophore X537A is added; in this case, only a partial polymerization of the actin occurs and the acrosomal vacuole does not fuse with the cell surface. The actin filaments that do form, however, are attached to the apical end of the actomere. In fact, the elongating filaments push their way into and frequently through the acrosomal vacuole. Thus, it appears that the sperm organizes the actin filaments by controlling their nucleation. My model is that the cell controls the ammount of unbound actin such that it is slightly above the critical concentration for polymerization. Then, spontaneous nucleation is unfavored and polymerization would proceed from existing nuclei such as the actomer.

Acrosome↗
PubMed1989

Fine tuning of polymerized pyridoxylated hemoglobin as a red blood cell substitute.

Hemoglobin (Hb), modified by pyridoxal 5'-phosphate (PLP) and polymerized by glutaraldehyde (GA) to yield polymerized pyridoxylated Hb (Poly-PLP-Hb), is currently the prime candidate for a hemoglobin-based red cell substitute. However, hematuria and excessive oxygen-binding affinity have been associated with poly-PLP-Hb after transfusion. These phenomena have not yet been explained. In the present communication, we show that pyridoxylation, which is known to reduce the oxygen-binding affinity of Hb to physiological levels, also inhibits the subsequent polymerization of Hb by GA. We attribute poly-PLP-Hb associated hematuria and high oxygen affinity to rapid elimination of these unpolymerized Hb species, leaving in the circulation the polymerized, less-highly pyridoxylated species with excessive oxygen-binding affinity. We proposed a mechanism for PLP inhibition of Hb polymerization, and discuss the implications of our findings for quality control in the preparation of poly PLP-Hb as a red cell substitute.

Blood Substitutes↗
PubMedDate not supplied

Microwave energy polymerization of poly(methyl methacrylate) denture base resin.

Several physical property tests were conducted to compare microwave energy and conventional hot water bath polymerization techniques. The two methods of polymerization produced similar dimensional accuracy in complete denture bases. No differences were found in transverse strength, Knoop hardness, density, and residual monomer content of resin test strips. Comparable strength was found between microwave-polymerized and autopolymerized repairs of resin test strips. No porosity was observed in complete or removable partial denture bases polymerized by either technique. The Knoop hardness of microwave-polymerized removable partial denture bases was found to be slightly lower near the metal framework.

Denture Bases↗
PubMed1989

[Effect of fluoride of copper and iron on polymerization of MMA/TBBO resin and adhesion to dentin].

As a model experiment to understand the mechanism of adhesion of the MMA/TBBO resin to dentin, polymerization of MMA/TBBO was investigated in the presence of a collagen sheet treated with the aqueous citric acid (CA) solutions of copper fluoride (CF), ferric fluoride (FF), or ferric chloride (FC), which is usually used as a treating agent in bonding of the resin to dentin. The curing time of MMA/TBBO resin was considerably reduced in the presence of collagen treated with CF-CA or FF-CA solutions when compared to that with FC-CA solution. Molecular weight of PMMA depended on the site of polymerization; PMMA polymerized inside the collagen sheet was the highest and that polymerized outside was the lowest. Bond strength to dentin treated with CF-CA, FF-CA solutions was as strong as that treated with FC-CA solution. Treatment of dentin with CF-CA or FF-CA was as effective as that with FC-CA in bonding the MMA/TBBO resin. These results suggested that ferric compounds adsorbed to collagen are involved in polymerization of MMA and thus influence bond strength of the MMA/TBBO resin to dentin.

Adhesiveness↗
PubMed1988

Polymerization of G-actin by myosin subfragment 1.

The polymerization of actin from rabbit skeletal muscle by myosin subfragment 1 (S-1) from the same source was studied in the depolymerizing G-actin buffer. The polymerization reactions were monitored in light-scattering experiments over a wide range of actin/S-1 molar rations. In contrast to the well resolved nucleation-elongation steps of actin assembly by KC1 and Mg2+, the association of actin in the presence of S-1 did not reveal any lag in the polymerization reaction. Light scattering titrations of actin with S-1 and vice versa showed saturation of the polymerization reaction at stoichiometric 1:1 ratios of actin to S-1. Ultracentrifugation experiments confirmed that only stoichiometric amounts of actin were incorporated into a 1:1 acto-S-1 polymer even at high actin/S-1 ratios. These polymers were indistinguishable from standard complexes of S-1 with F-actin as judged by electron microscopy, light scattering measurements, and fluorescence changes observed while using actin covalently labeled with N-(1-pyrenyl)iodoacetamide. F-actin obtained by polymerization of G-actin by S-1 could initiate rapid assembly of G-actin in the presence of 10 mM KC1 and 0.5 mM MgCl2 and showed normal activation of MgATPase hydrolysis by myosin.

Actins↗
PubMed1988

Cooperative effect of tumor necrosis factor and gamma-interferon on chemotactic peptide receptor expression and stimulus-induced actin polymerization in HL-60 cells.

We studied the effect of tumor necrosis factor (TNF) and gamma interferon (IFN-gamma), alone and in combination, on the expression of chemotactic peptide receptors, stimulus-induced actin polymerization, hydrogen peroxide production (H2O2), and expression of nonspecific esterase (NSE) positivity in human promyelocytic leukemic cell line HL-60. These parameters were analyzed following a five-day culture with the cytokines. Chemotactic peptide receptor expression was studied using the fluoresceinated hexapeptide, formyl-norleucyl-leucyl-phenylalanyl-norleucyl-tyrosyl-lysine and flow cytometry. Actin polymerization, an important event required for chemotaxis and phagocytosis, was studied using NBD-phallacidin labeling, following stimulation with the chemotactic peptide formyl-methionyl-leucyl-phenylalanine (FMLP) or phorbol myristate acetate (PMA). TNF increased the expression of chemotactic peptide receptors in a dose-dependent fashion, and there was good correlation between the receptor expression, stimulus-induced actin polymerization, H2O2 production, and NSE positivity. IFN-gamma was less potent in inducing all the parameters studied but exerted a positive cooperative effect when combined with TNF. IFN-gamma at high concentrations induced chemotactic peptide receptors comparable in magnitude to that seen with TNF but failed to prime these cells to undergo actin polymerization in response to FMLP or PMA. Undifferentiated HL-60 cells showed a decrease in F-actin content on stimulation with PMA. This suggests that protein kinase C might have a negative regulatory role in stimulus-induced actin polymerization. The observations reported here indicate that appropriate combinations of different inducing agents with different modes of action might be necessary to duplicate the functional abilities of mature phagocytic cells.

Actins↗