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The relationship between factor VII coagulant activity and factor XII activation induced in plasma by endogenous or exogenously added contact surface.

The contribution of various enzymes in the activation of factor VII, determined from the increase in factor VII coagulant activity (VIIc), was investigated following the exposure of citrated plasma to low temperature. The contact system of coagulation was initiated either by the contact surface present in certain plasmas (i.e. plasma from women in late pregnancy) or by micellar stearate added to plasma diluted with an equal volume of buffer (plasma from normal healthy subjects or from women in late pregnancy). With either of the contact surfaces, increase of VIIc and the concentration of enzymes derived from factor XII (XIIa) depended on the potency of the contact surface. The stearate-induced VIIc in diluted plasmas from women in late pregnancy or from normal subjects was inhibited by 60-70% in the presence of anti-factor IX monoclonal antibody. VIIc was not increased in XII-deficient plasma following the addition of stearate. The addition of purified human factor XII to this plasma restored the increase in VIIc and the activation of factor XII. In factor IX-deficient plasma, the stearate-induced increase in VIIc was only 38% of that seen in normal plasma and was restored by the addition of purified factor IX. Similarly in factor XI-deficient plasma, the stearate-induced increase in VIIc and the factor XII activation were 48% and 69% of that found in normal plasma. The addition of EDTA (2 mM) did not alter the extent of factor XII activation induced by contact surface, but it did inhibit the rise in VIIc. It is concluded that in the presence of contact surface the activation of factor XII and the sequential activation of factor XI and of factor IX results in the activation of factor VII. Activated factor IX is responsible for the major part of the factor VII activation whereas the rest may be through the direct activation by XIIa.

Antibodies, Monoclonal↗

Ribozymes targeted to stearoyl-ACP delta9 desaturase mRNA produce heritable increases of stearic acid in transgenic maize leaves.

Ribozymes are RNAs that can be designed to catalyze the specific cleavage or ligation of target RNAs. We have explored the possibility of using ribozymes in maize to downregulate the expression of the stearoyl-acyl carrier protein (Delta9) desaturase gene. Based on site accessibility and catalytic activity, several ribozyme constructs were designed and transformed into regenerable maize lines. One of these constructs, a multimer hammerhead ribozyme linked to a selectable marker gene, was shown to increase leaf stearate in two of 13 maize lines. There were concomitant decreases in Delta9 desaturase mRNA and protein. The plants with the altered stearate phenotype were shown to express ribozyme RNA. The ribozyme-mediated trait was heritable, as evidenced by stearate increases in the leaves of the R1 plants derived from a high-stearate line. The increase in stearate correlated with the presence of the ribozyme gene. A catalytically inactive version of this ribozyme did not produce any significant effect in transgenic maize. This is evidence that ribozymes can be used to modulate the expression of endogenous genes in maize.

Amino Acid Sequence↗

Effect of lubricant type and concentration on the punch tip adherence of model ibuprofen formulations.

A model formulation, comprising ibuprofen and direct compression lactose (Tablettose 80) was used to assess the influence of two lubricants, magnesium stearate and stearic acid, on punch tip adherence. Lubricant concentrations were varied from 0.25% to 2% w/w. Formulations in the presence and absence of 0.5% w/w colloidal silica (Aerosil 200) were examined, to assess the influence of the glidant on the anti-adherent effects of the lubricants. Differential scanning calorimetry (DSC) was used to examine the effect of the lubricants on the melting temperature of ibuprofen. Tablets were compacted using a single punch tablet press at 10 kN using hard chrome-plated punches or at 40 kN using uncoated steel punches, tooling was 12.5-mm diameter in each case. The upper punch faces were characterized by obtaining Taylor Hobson Talysurf surface profiles. Following compaction, ibuprofen attached to the face was quantified by spectroscopy. At low concentrations of each lubricant, the levels of sticking observed were similar. Whilst sticking increased at magnesium stearate concentrations above 1%, sticking with stearic acid remained relatively constant at all concentrations. DSC revealed that the melting temperature of ibuprofen was lowered by the formation of eutectic mixtures with both lubricants. However, the onset temperature of melting and melting point were lowered to a greater extent with magnesium stearate compared with stearic acid. When using uncoated tooling at 40 kN, the deleterious effects of magnesium stearate on the tensile strength of the tablets also contributed to sticking. When using chrome-plated punches at 10 kN, the tensile strength reduction by the presence of magnesium stearate was less pronounced, as was the level of sticking.

Adhesiveness↗

[A study of the properties of compacts from a mixed dry binder on the base of alpha-lactose monohydrate and microcrystalline cellulose].

The paper studies the tensile strength and disintegration time of compacts from the mixed dry binder MicroceLac 100. Tensile strength and disintegration time of tablets were tested in connection with the following factors: compression force, compression rate, addition of magnesium stearate, addition of ascorbic acid, the model active principle. The compression forces employed were 5, 6, and 7 kN, compression rates, 20 and 40 mm/min, stearate concentration 0, 0.4, and 0.8%, ascorbic acid concentration, 25 and 50%. With increasing addition of the stearate, the strength of compacts from MicroceLacu 100 was decreased for both compression rates, but with a higher rate, in a concentration of 0.4%, the decrease in strength was more marked. Disintegration time was increased with compression force and the addition of the stearate, but in all cases it was very short. Increased addition of ascorbic acid further intensified the decrease in the strength of compacts and decreased the disintegration time and the effect of the stearate on it. Disintegration time of compacts with ascorbic acid in a concentration of 50% did not increase with compression force.

Cellulose↗

Permeation of long-chain fatty acid into adipocytes. Kinetics, specificity, and evidence for involvement of a membrane protein.

This study extends our earlier work (Abumrad, N. A., Perkins, R.C., Park, J.H., and Park, C.R. J. Biol. Chem. 256, 9183-9191) which showed that oleate permeates the plasma membrane of the rat adipocyte principally by a transport process with the characteristics of facilitated diffusion. In the present study, fatty acid (FA) transport is characterized with regard to its specificity and susceptibility to inhibition by protein modifiers. The kinetics of competitive inhibition for transport of oleate and stearate are shown under conditions where complications due to competition for binding of FAs to the albumin in the medium are minimized. Stearate inhibits influx of tracer oleate with a Ki that closely approximates its Km and, conversely, oleate inhibits similarly the influx of tracer stearate. Specificity of the FA transport system is shown in studies using a variety of natural FAs of different chain length, or FA analogues. Oleate (Km = 0.06 microM), stearate (Km = 0.16 microM), linoleate (Km = 0.22 microM), palmitate, (Km = 0.2 microM), and laurate (Km = 1.5 microM) are good substrates, but octanoate is not transported. An oxazolidine ring on C-5 but not on C-16 of stearate blocks binding to the transporter. Methylation of the carboxyl function but not alpha-bromination inhibits transport. These studies suggest that a FA must have a hydrocarbon chain of at least nine carbons and a free carboxyl function to be recognized by the transporter. FA transport does not require Na or ATP. Pronase but not trypsin treatment of intact cells reduces fatty acid influx. Transport is insensitive to maleimides. It is strongly and irreversibly blocked by pretreatment of the cells with the stilbene compounds, 4,4'-diisothiocyanostilbene-2,2'-disulfonate and 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid, but only slightly inhibited by dipyridamole. Polyacrylamide gel electrophoresis of plasma membrane proteins from cells treated with [3H] 4,4'-diisothiocyanostilbene-2,2'-disulfonate shows a peak of radioactivity at about Mr = 85,000. When cells are incubated in various concentrations of this agent, the counts recovered in the peak reach a maximum coincident with maximum inhibition of transport. We conclude that permeation of the plasma membrane of the adipocyte by long-chain FAs at physiological concentrations is mediated by a protein transporter with distinct specificity requirements.

Adipose Tissue↗

Effects of a tristearate-containing lipid and canola oil on plasma and tissue lipids in rats.

Male Sprague-Dawley rats were fed semipurified diets containing 12% fat and 0.4% cholesterol for 4 wk. The fats were palm oil, a high-stearate fat and canola oil; each of the latter two fat sources was substituted for palm oil in 4% (w/w) increments (i.e, 4, 8 and 12%) thus yielding 3 stearate-containing, 3 canola-containing, and a 12% palm oil diet. Stearate-fed animals exhibited significantly decreased food efficiency ratios, plasma total cholesterol, and liver cholesterol whereas the substitution of canola for palm oil did not consistently alter these parameters. Liver fatty acids generally reflected the composition of the dietary fat sources with the exception of significantly higher arachidonate observed in the stearate-fed rats.

Animals↗

Effects of aliphatic fatty acids on the binding of Phenol Red to human serum albumin.

Binding of Phenol Red to human serum albumin at pH 7.0 was studied by ultrafiltration (n1 = 1, K1 = 3.9 X 1-(4) M-1, n2 = 5, K2 = 9.6 X 10(2) M-1). The presence of 1 mol of octanoate or decanoate per mol of albumin caused a decrease in dye binding (dye/protein molar ratio 1:1), which, in contrast with additional fatty acid, was very pronounced: 1-8 mol of palmitate or stearate resulted in a small, and apparently linear, displacement of Phenol Red. The displacement effect of 1-5 mol of oleate, linoleate or linolenate per mol of albumin was comparable with that of the equimolar concentrations of palmitate or stearate. A higher molar ratios the unsaturated acids caused a drastic decrease in dye binding. The different Phenol Red-displacement effects of low molar ratios of medium-chain and long-chain fatty acids indicate that these acids have different high-affinity binding sites. In accordance with this proposal, low concentrations of stearate had only a small effect on the Phenol Red-displacement effect of octanoate. Phenol Red-binding curves in the presence of 1 mol of octanoate, 8 mol of stearate and 6 or 7 mol of linolenate per mol of albumin respectively indicated that the dye and the fatty acids do not complete for a common primary binding site. In contrast, a secondary Phenol Red-binding site could be identical with the primary octanoate-binding site. Furthermore, the primary Phenol Red-binding site could be the same as a secondary linolenate-binding site. Assignment of the different primary binding sites for Phenol Red and for medium-chain and long-chain fatty acids to a model of the secondary structure of albumin is attempted.

Binding Sites↗

The peroxisomal proliferator clofibrate enhances the hepatic cytoplasmic movement of fatty acids in rats.

The role of cytosolic fatty acid binding protein (FABP) in cellular fatty acid metabolism remains poorly defined. The intracellular movement of fatty acids is thought to be facilitated through codiffusion with FABP. Peroxisomal proliferators like clofibrate induce FABP and may stimulate fatty acid use by increasing cytoplasmic diffusion rates. Our aim was to determine if induction of FABP by clofibrate increases the cytoplasmic transport of a fluorescent fatty acid NBD-stearate. Male rats were fed clofibrate for 9 days to increase the hepatic concentration of FABP. Hepatocytes were isolated using collagenase perfusion. Cytosolic FABP was measured by enzyme-linked immunosorbent assay (ELISA) using a specific antibody to hepatic FABP. Two-dimensional laser photobleaching (FRAP) was used to measure the cytoplasmic movement of NBD-stearate in hepatocytes. Cytoplasmic transport of NBD-stearate occurred by isotropic diffusion with no evidence for convective or directed transport. Treatment with clofibrate increased FABP levels, the fraction of NBD-stearate found in cytosol, and the observed cytoplasmic diffusion rate. The increase in cytoplasmic movement exceeded that predicted from FABP binding changes suggesting that clofibrate also enhances fatty acid diffusion within intracellular membranes. Nonspecific effects of clofibrate on cytoplasmic viscosity or pore size were not observed. These data suggest that clofibrate treatment induces cytosolic FABP and stimulates the intracellular movement of fatty acids by 2 distinct mechanisms. Soluble proteins like FABP promote the cytoplasmic transport of fatty acids by increasing diffusion. These data further support a role for intracellular binding proteins in facilitating the intracellular movements of fatty acids.

4-Chloro-7-nitrobenzofurazan↗

Mass spectrometric analysis of GAP-43/neuromodulin reveals the presence of a variety of fatty acylated species.

GAP-43 (neuromodulin) is a protein kinase C substrate that is abundant in developing and regenerating neurons. Thioester-linked palmitoylation at two cysteines near the GAP-43 N terminus has been implicated in directing membrane binding. Here, we use mass spectrometry to examine the stoichiometry of palmitoylation and the molecular identity of the fatty acid(s) attached to GAP-43 in vivo. GAP-43 expressed in either PC12 or COS-1 cells was acetylated at the N-terminal methionine. Approximately 35% of the N-terminal GAP-43 peptides were also modified by palmitate and/or stearate on Cys residues. Interestingly, a variety of acylated species was detected, in which one of the Cys residues was acylated by either palmitate or stearate, or both Cys residues were acylated by palmitates or stearates or a combination of palmitate and stearate. Depalmitoylation of membrane-bound GAP-43 did not release the protein from the membrane, implying that additional forces function to maintain membrane binding. Indeed, mutation of four basic residues within the N-terminal domain of GAP-43 dramatically reduced membrane localization of GAP-43 without affecting palmitoylation. These data reveal the heterogeneous nature of S-acylation in vivo and illustrate the power of mass spectrometry for identification of key regulatory protein modifications.

Acylation↗

Cytoplasmic codiffusion of fatty acids is not specific for fatty acid binding protein.

The intracellular movement of fatty acids is thought to be facilitated through codiffusion with fatty acid binding protein (FABP). Previous work suggested that FABP decreases fatty acid binding to immobile membranes, causing faster cytoplasmic diffusion. However, the specificity for binding to FABP has not been addressed. The aim of the current study was to determine whether specific FABP binding is required or whether binding to other proteins will produce the same effect. A model cytoplasm consisted of a fatty acid, proteins, and liposomes to simulate intracellular membranes. Laser photobleaching (fluorescence recovery after photobleaching) was used to measure the movement of the fluorescent fatty acid 12-N-methyl-7-nitrobenzo-2-oxa-1,3-diazoaminostearate (NBD-stearate) in model cytoplasm, in normal and permeabilized Hep G2 cells, and after incubation of permeabilized cells with bovine serum albumin (BSA) or FABP. Increasing protein in the model cytoplasm increased the diffusion rate in proportion to the extent of protein binding. Cell permeabilization reduced diffusion of NBD-stearate to < 5% of controls. Incubation of permeabilized cells with FABP or BSA resulted in a concentration-dependent increase in the NBD-stearate diffusion rate. BSA was more effective than FABP in binding NBD-stearate and increasing its diffusion rate after permeabilization. Proteins like FABP promote the diffusion of fatty acids. Removal of these proteins drastically reduces cytoplasmic diffusion. Substitution with BSA reestablishes the diffusive flux, suggesting that specific binding to FABP is not required. These data support a role for intracellular binding proteins in facilitating the cytoplasmic movement of fatty acids.

4-Chloro-7-nitrobenzofurazan↗

Saturable stimulation of fatty acid transport through model cytoplasm by soluble binding protein.

To better define the role of soluble binding proteins in the cytoplasmic transport of amphipathic molecules, we measured the diffusional mobility of a fluorescent long-chain fatty acid, 12-N-methyl-(7-nitrobenz-2-oxa-1,3-diazol)aminostearate (NBD-stearate), through model cytoplasm as a function of soluble binding protein concentration. Diffusional mobilities were correlated with the partition of the fatty acid between membrane and protein binding sites. Cytoplasm was modeled as a dense suspension of liposomes, and albumin was used as a model binding protein. Albumin saturably increased NBD-stearate mobility through the membrane suspension approximately eightfold. Fatty acid mobility in the absence of albumin was identical to the mobility of the membrane vesicles (1.99 +/- 0.33 x 10(-8) cm(2)/s), whereas the mobility at saturating concentrations was identical to the mobility of albumin (1.65 +/- 0.12 x 10(-7) cm(2)/s). The protein concentration producing half-maximal stimulation of NBD-stearate diffusion (42.8 +/- 0.3 microM) was unexpectedly greater than that required to solubilize half of the NBD-stearate (17.9 +/- 3.0 microM). These results support a proposed mechanism for cytoplasmic transport of small amphipathic molecules in which aqueous diffusion of the protein-bound form of the molecule largely determines the transport rate. However, slow interchange of fatty acid between the binding protein and membranes also appears to influence the transport rate in this model system.

4-Chloro-7-nitrobenzofurazan↗

Cytoplasmic transport of fatty acids in rat enterocytes: role of binding to fatty acid-binding protein.

The intracellular movement of fatty acids is thought to be facilitated through codiffusion with fatty acid-binding protein (FABP). This facilitation may occur by decreasing binding to immobile membranes, leading to faster cytoplasmic diffusion. The aims of this study were to measure the intracellular transport of 12-N-methyl-(7-nitrobenzo-2-oxa-1,3-diazol)aminostearate (NBD-stearate) in villus rat enterocytes and to determine 1) the mechanism of its cytoplasmic transport and 2) if its transport rate correlated with the known variation of FABP binding capacity along the length of the small intestine. Two-dimensional laser photobleaching was used to measure the movement of a fluorescent fatty acid NBD-stearate in enterocytes isolated from different segments of rat intestine. The fraction of NBD-stearate found in the cytostol of enterocytes was determined by differential centrifugation. Cytoplasmic transport of NBD-stearate occurred solely by diffusion and not by convection. Diffusion was homogeneous (nondirectional), consistent with isotropic diffusion. The diffusion rate varied with location along the intestine, correlating with the local FABP concentration and measured cytosolic binding. We conclude that cytoplasmic proteins like FABP promote the intracellular transport of fatty acids by enhancing their diffusive flux. We suggest that facilitation is not specific for a particular cell type but occurs in a variety of cells that transport fatty acids and may contain different types of FABP.

4-Chloro-7-nitrobenzofurazan↗

The use of 8-anilino-1-naphthalenesulfonic acid as a reporter group molecule for circular dichroism and fluorescence measurements. The effect of stearic acid and sodium dodecylsulfate on the conformation of bovine and human serum albumin.

The fluorescence probe ANS(8-anilino-1-naphthalenesulfonic acid) was employed as a reporter group molecule for circular dichroism and fluorescence measurements in order to investigate the effects of stearic acid and sodium dodecylsulfate on the conformation of bovine and human serum albumin. Stearate as well as dodecylsulfate displaces ANS from the binding to both albumins. Besides this displacement, stearate and dodecylsulfate influence the fluorescence properties and the extrinsic Cotton effects on ANS bound to both albumins. It is suggested that the origin of these effects is a microdisorganization of the albumin structure, provoked by the binding of stearate and sodium dodecylsulfate. Each of the four extrinsic CD bands of bound ANS was influenced in a different manner by the addition of stearate and dodecylsulfate. Using the data of the fluorescence measurements and of the circular dichroism measurements it was possible to differentiate the effects of one ligand on both albumins and of both ligands on one albumin more efficiently than would have been possible using one of the two methods alone. It is suggested that the use of ANS as a reporter group molecule for fluorescence and circular dichroism measurements is a very good tool to detect small changes in the environment of ligand binding sites on protein molecules.

Anilino Naphthalenesulfonates↗

Electron microscope characterization of AgBr heterojunctions with silver carboxylates and their influence on the morphology of developed silver particles in thermally developed photomaterials.

Silver halide crystals formed during in situ treatment of silver stearate crystals with various halidizing agents are observed by scanning and transmission electron microscopy to form on the lateral edges of the silver carboxylate crystals. The location of the silver halide phase on the crystal edge is dictated by the anisotropic structure of the silver stearate crystal lattice, specifically, the layered structure in which silver ion layers are separated by long-chain hydrocarbon groups. The formation of AgBr on the lateral faces of these crystals is proposed to be typical not only of the formation of silver halide on silver stearate but also for all silver carboxylates of the general formula [AgCnH2(n-1)O2]2 when the crystals of these silver carboxylates have anisotropic, layered structures. The silver bromide/silver carboxylate heterojunction in an in situ system has been clearly observed by transmission electron microscopy. The heterojunction is comprised of a distorted silver carboxylate lattice, which accommodates the misalignment between the AgBr and [Ag(O2CR)]2 crystal lattices. The nature of heterojunction between the AgBr and the silver carboxylate when the AgBr is prepared separately from the preparation of the silver carboxylate differs from the in situ heterojunction. In this case, a layered compound, proposed to have a Ag1-xNaxSt composition, forms between the AgBr and the silver stearate which is a unique feature of this interface. The differences in the structure of interfaces formed between the silver halide and the silver fatty acid complex result in different silver particle morphologies during thermal development of exposed photothermographic films. The developed silver is generally filamentary when the photothermographic material contains silver halide prepared by the in situ exchange reaction between silver carboxylate and a brominating agent. If the photothermographic material is prepared from previously synthesized silver halide crystals, the preformed AgBr route, the developed silver generally crystallizes as dendritic crystals.

Bromides↗

Solid-state stability of aspirin in the presence of excipients: kinetic interpretation, modeling, and prediction.

Salicylsalicylic acid and acetylsalicylsalicylic acid were identified as decomposition products of aspirin when mixtures of the drug, with magnesium stearate, were stored in the solid state of 60 degrees and 75% relative humidity. The effect of increasing the concentration of magnesium stearate and the addition of other alkali stearates on the rate of decomposition of aspirin were studied. The validity of the theory that pH changes induced by the alkali stearates account for the catalytic effect of the lubricants on the decomposition was tested. The changes observed were modeled and the mechanism involved elucidated. The potential use of the melting points of aspirin mixtures in predicting the stability of the drug in such drug-excipient mixtures is demonstrated.

Aspirin↗

Differential, temporal and spatial expression of genes involved in storage oil and oleosin accumulation in developing rapeseed embryos: implications for the role of oleosins and the mechanisms of oil-body formation.

The temporal and spatial expression of oleosin and delta 9-stearoyl-ACP desaturase genes and their products has been examined in developing embryos of rapeseed, Brassica napus L. var. Topas. Expression of oleosin and stearate desaturase genes was measured by in situ hybridisation at five different stages of development ranging from the torpedo stage to a mature-desiccating embryo. The temporal pattern of gene expression varied dramatically between the two classes of gene. Stearate desaturase gene expression was relatively high, even at the torpedo stage, whereas oleosin gene expression was barely detectable at this stage. By the stage of maximum embryo fresh weight, stearate desaturase gene expression had declined considerably while oleosin gene expression was at its height. In contrast to their differential temporal expression, the in situ labelling of both classes of embryo-specific gene showed similar, relatively uniform patterns of spatial expression throughout the embryo sections. Immunogold labelling of ultra-thin sections from radicle tissue with anti-oleosin antibodies showed similar patterns to sections from cotyledon tissue. However, whereas at least three oleosin isoforms were detectable on western blots of homogenates from cotyledons, only one isoform was found in radicles. This suggests that some of the oleosin isoforms may be expressed differentially in the various types of embryo tissue. The differential timing of stearate desaturase and oleosin gene expression was mirrored by similar differences in the timing of the accumulation of their ultimate products, i.e. storage oil and oleosin proteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Brassica↗

Erythromycin resistance in mouse L cells.

The sensitivity of mouse cell lines in culture to the macrolide antibiotic, erythromycin stearate, was investigated. Both resistant and sensitive lines were found. Experiments indicated that in sensitive cells erythromycin stearate inhibits mitochondrial protein synthesis. Mutants resistant to erythromycin stearate were selected from the line LM(TK-), and these are also less sensitive to other macrolide antibiotics such as carbomycin and spiramycin. Attempts to transfer the erythromycin resistance of either the mutants or naturally resistant lines by fusion of cytoplasts with sensitive cells were unsuccessful, and it is concluded that resistance to erythromycin stearate is controlled by nuclear genetic factors.

Animals↗

Selective use of palmitic acid over stearic acid for synthesis of phosphatidylcholine and phosphatidylglycerol in lung.

The incorporation of [3H]palmitic acid and [14C]stearic acid into phospholipids in rabbit lung tissue was studied. Under equal molar concentrations of palmitate and stearate, palmitate was incorporated to the 1- and 2-positions of phosphatidylcholine (PC) and phosphatidylglycerol (PG) 2-3 times more than stearate. By contrast, palmitate was 30% less than stearate in phosphatidylethanolamine, phosphatidylinositol and phosphatidylserine. These results suggest that preferential utilization of palmitate over stearate, rather than substrate availability, determines the high content of palmitoyl at the 1- and 2-positions of PC and PG in lung.

Animals↗