Effect of oleic and linoleic acids on the monodesaturation in vitro of stearic acid by the livers of patients suffering from malignant neoplastic diseases.
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Carbon Isotopes↗
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Results for “STEARIC ACID”
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Stearic acid as plasma replacement for intracellular in vitro culture of Plasmodium knowlesi.
A chloroform extract of Cohn's fraction IV-4 of human plasma successfully replaced whole fraction IV-4 for the intracellular in vitro culture of Plasmodium knowlesi. We are now able to report the successful replacement of monkey plasma by stearic acid.
Animals↗
Relaxation behaviors of monolayers of octadecylamine and stearic acid at the air/water interface.
This study investigated the relaxation behaviors of octadecylamine (ODA), stearic acid (SA), and SA/ODA mixed monolayers at the air/water interface. Area relaxations of monolayers at constant surface pressure were studied by a nucleation and growth mechanism and by direct observation using a Brewster angle microscope (BAM). The results showed that ODA and SA monolayers exhibit different characteristics in the area loss and in the BAM morphology. In the initial relaxation stage, SA monolayer illustrates a more stable characteristic than ODA. But at the later stage, the area loss of SA monolayer increases more quickly than that for ODA due to significant nucleation and growth of 3D aggregates. The BAM results demonstrated that 3D aggregates of large scale domains are likely to form on a SA monolayer even when the area loss is insignificant. On the contrary, only dotlike aggregates of low density were found on the ODA monolayer when relaxation is carried out at higher surface pressure. The relaxation behavior of SA monolayer can be described by the Vollhardt model. However, the relaxation of ODA monolayer does not follow the nucleation model described by Vollhard but can reasonably be attributed to the effect of dissolution. For the SA/ODA mixed monolayers, the relaxation behaviors in the initial and final stages follow different mechanisms, which is attributed to the formation of distinct phases as observed from the BAM. This result also implied that SA and ODA are not completely miscible to be a homogeneous phase. Phases of various compositions were formed in the mixed monolayers, and thus, the relaxation mechanism was shifted during the relaxation process as dominated by different relaxation behaviors of various phases.
Journal Article↗
Studies on the structure and miscibility of mixed Langmuir-Blodgett films of a double-armed dibenzo-18-crown-6 ether with stearic acid.
Reported here is the study on the structure of Langmuir-Blodgett (LB) films of double-armed dibenzo-18-crown-6 contain biphenyl (DACE) which are newly synthesized and mixed with stearic acid (SA). In addition, the miscibility of the two compounds was also tested by the measurement of the surface pressure-area (pi-A) isotherms of DACE and DACE/SA with various proportions. It is noted that there is no phase segregation in the mixed monolayer film of DACE/SA. Upon calculation of the excess surface area, it is concluded that the SA molecule can enter into the crown ether ring, while an 18C6 ring can host a maximum of one SA molecule. The difference of spectroscopic properties of DACE in LB films and bulk solution has been investigated by ultraviolet-visible (UV-vis) and Fourier-transfer infrared (FTIR) measurements. Molecules of DACE exist in the mixed LB films as monomers in contrast to those in the concentrated solution as aggregates. The hydrocarbon chains in DACE and DACE/SA LB films are tilted to the normal of the substrate surface, but perpendicular to the dipole moment of CO. Both CO bonds in the phenyl ethers and carboxylic ester of DACE, and the long axes of phenyl rings are aligned nearly perpendicular to the substrate surface. Infrared spectra of mixed LB films of DACE/SA present further evidence that the SA molecules enter into the crown ether rings of DACE.
Colloids↗
Effects of dietary stearic acid on plasma cholesterol levels.
Dietary advice based on saturated versus unsaturated fatty acids for the purpose of controlling the plasma cholesterol level has for many years plagued the American public with unpalatable diets that are difficult to adhere to. Stearic acid, an 18-carbon saturated fatty acid, does not share the hypercholesterolemic effect of other saturated fatty acids and may be the key to more palatable diets for the cholesterol-conscious dieter in the future.
Cholesterol↗
CHAIN-SHORTENING OF STEARIC ACID IN THE INTACT RAT.
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Acetates↗
THE CONVERSION OF STEARIC ACID TO OLEIC IN FRESHLY SECRETED MILK.
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Animals↗
Lysozyme-glucose stearic acid monoester conjugate formed through the Maillard reaction as an antibacterial emulsifier.
Lysozyme-glucose stearic acid monoester (HEL-GE) conjugate was prepared through the Maillard reaction as an antibacterial emulsifier. The molar ratio of GE to HEL was 1:1. The isoelectric point was 6-7, which is lower than that of native HEL. Spectroscopic studies indicated that the alpha-helix content was slightly lower but the conformation around Trp had not changed and that the surface of the conjugate was covered with the GE moiety. The conjugate maintained approximately 53-57% of the enzymatic activity of native HEL at 40-60 degrees C and exhibited considerable resistance to proteolysis. The denaturation temperature of the conjugate was approximately 74 degrees C, somewhat higher than that of control HEL, whereas the enthalpy was about one-third of that of control HEL. The emulsifying activity of the conjugate and the emulsion stability were much enhanced compared to those of native HEL, and the conjugate maintained approximately 70% of the bactericidal activity.
Anti-Bacterial Agents↗
Conversion of first and sixth carbons of stearic acid to carbon dioxide by rats.
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Animals↗
Dietary fat induces changes in factor VII coagulant activity through effects on plasma free stearic acid concentration.
Previous studies have demonstrated activation of the contact system of coagulation and an increase in factor VII coagulant activity (VIIc) when citrated plasma is incubated in the presence of micellar stearate. The products of contact activation, factors XIIa and IXa, were responsible in this system for the activation of factor VII, thereby increasing factor VIIc. To obtain evidence that these in vitro interactions also operate in vivo, factor VIIc was examined in relation to plasma free fatty acid concentrations in five healthy individuals during the consumption of isocaloric high-saturated fat, high-unsaturated fat, and low-fat diets, each taken for 4 weeks in random order and separated by intervals of 12 weeks. For all but the final 3 days of each phase, subjects selected appropriate foods from prepared lists to meet the dietary requirements. Experimental diets of predetermined fat content and composition were fed on days 26 through 28 in each phase. Fat supplied on average 62% of energy in two of the experimental diets and less than 20% of energy in the third. On the final day of each dietary phase, the concentrations of the various free fatty acids and factor VIIc were measured before breakfast and at three 150-minute intervals thereafter. Plasma factor VIIc was, respectively, 6.5% and 13.1% of standard higher on the unsaturated and saturated fat diets than on the low-fat diet. Furthermore, the plasma concentration of stearic acid was strongly associated with factor VIIc (r = .58; P < .0001), and this relation remained significant (P = .003) after allowance for the plasma concentrations of palmitic, oleic, and linoleic acids.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Effect of dicetylphosphate or stearic acid on spontaneous transfer of protein from influenza virus-infected cells to dimyristoylphosphatidylcholine liposomes.
Membrane proteins, such as viral spike, were transferred spontaneously from influenza virus-infected cells to various liposomes. The protein transfer was enhanced by the presence of negative charged component dicetylphosphate (DCP) or stearic acid (SA) in dimyristoylphosphatidylcholine (DMPC) liposomes. The lowering of membrane fluidity did not relate to the effect of DCP or SA on protein transfer in this study. We considered that the alteration of membrane properties, such as construction of the surface or stability of transferred protein in liposomes, due to the specific structure of DCP or SA is responsible for the enhancement of spontaneous protein transfer by the presence of the amphiphilic components.
Animals↗
Effect of UVA radiation on membrane fluidity and radical decay in human fibroblasts as detected by spin labeled stearic acids.
The ultraviolet A (UVA) radiation component of sunlight (320-400 nm) has been shown to be a source of oxidative stress to cells via generation of reactive oxygen species. We report here some consequences of the UVA irradiation on cell membranes detected by electron paramagnetic resonance (EPR) spectroscopy. Paramagnetic nitroxide derivatives of stearic acid bearing the monitoring group at different depths in the hydrocarbon chain were incorporated into human fibroblasts membranes to analyze two main characteristics: kinetics of the nitroxide reduction and membrane fluidity. These two characteristics were compared for control and UVA-irradiated (0-250 kJ/m(2)) cells. The term relative redox capacity (RRC) was introduced to characterize and to compare free radical reduction measured by EPR with some well-known viability/clonogenicity tests. Our results showed that UVA-irradiation produces a more rigid membrane structure, especially at higher doses. Furthermore, we found that trends agree in survival measured by neutral red (NR), trypan blue (TB), and clonogenic efficiency compared with RRC values measured by EPR for low and medium exposure doses. Above 100 kJ/m(2), differences between these tests were observed. Antioxidant effect was modeled by alpha-tocopherol-acetate treatment of the cells before UVA irradiation. While NR, TB and clonogenicity tests showed protection at the highest UVA doses (>100 kJ/m(2)), results obtained with EPR measurements, both membrane fluidity and kinetics, or using MTT test did not exhibit this protective effect.
Cell Line↗
[Hepatic microsomal delta 9 desaturation of stearic acid in the spontaneously diabetic female BB rat].
delta 9 desaturation of stearic (1-14C) acid has been estimated from incubation of liver microsomes of adult female spontaneously diabetic BB rat, an animal model resembling the spontaneous juvenile diabetes in humans, comparatively to adult female control Wistar rat. The animals were sacrificed, when hyperglycemic, 24 hours after the last insulin injection to the BB rats. Stearic acid delta 9 desaturase activity is drastically depressed in the BB rats when fatty acid composition of liver phospholipids and microsomal total liver lipids are changed in spite of the daily injection of insulin necessary for the BB rats survival.
Animals↗
Effects of fatty ethers and stearic acid on the gastrointestinal absorption of insulin.
Insulin degradation and inactivation occurs when the protein is given to an animal through oral route. The following compounds were assessed to determine their potential effect in increasing insulin absorption: polyoxyethylene (20) oleyl ether (Brij 99), polyoxyethylene lauryl ether and polyoxyethylene (20) cetyl ether (Brij 58). In this study the above compounds, along with stearic acid, were used to prepare granules with or without addition of insulin and were given orally to rabbits. Both glucose and insulin levels in blood were measured at different time intervals, the former with a glucometer and the latter using radioimmunoassay (RIA). To determine if there was a relationship between the glucose and the insulin levels in blood, a highly sensitive radioimmunoassay method was used to detect any small changes in the level of insulin in blood. A significant decrease in glucose blood levels (P less than 0.05) was obtained after oral administration of each of granules containing insulin. The greatest reduction was observed after half an hour of the oral administration of the granules. A similar response was obtained with the hypodermal injection of 1/5 of the oral insulin dose. Granules prepared with Brij 58 and containing insulin was the only formula that showed increase of insulin level in the blood. This was equivalent to 1/10 of the change produced after hypodermal injection of the hormone. In these experiments the changes in blood insulin levels were not directly proportional to the corresponding changes in blood glucose.
Animals↗
Chain orientation and headgroup structure in Langmuir monolayers of stearic acid and metal stearate (Ag, Co, Zn, and Pb) studied by infrared reflection-absorption spectroscopy.
The monolayers of stearic acid at the air-water interface on pure water and ion-containing subphases have been studied using infrared reflection-absorption spectroscopy. In the presence of Co(2+), Zn(2+), and Pb(2+), ordered hydrocarbon chains and hexagonal subcell structure remain almost unchanged in comparison with those for the monolayer on pure water at the surface pressure of 20 m/Nm. In the cases of Co(2+) and Zn(2+), the H-bonded monodentate and unsymmetric bidentate chelating structure within the headgroups were formed, and in the case of Pb(2+), three types of structures, bidentate chelating, unsymmetric chelating, and bidentate bridging coordinations, were formed. The hydrocarbon chains in the monolayers are uniaxially oriented at a tilt angle of approximately 0 degrees with respect to the surface normal in contrast to a tilt angle of approximately 20 degrees on pure water surface at 20 m/Nm by the computer simulation of theoretical calculation to experimental data. In the presence of Ag(+), multilayers were developed with the highly ordered hydrocarbon chains in a triclinic subcell structure and a bidentate bridging structure within the headgroups. The multilayers were composed of three monolayers and the hydrocarbon chains in each monolayer were oriented at an angle of approximately 30 degrees away from the surface normal with their C-C-C planes almost perpendicular to the water surface.
Journal Article↗
Effects of composition, moisture and stearic acid on the plasto-elasticity and tableting of paracetamol-microcrystalline cellulose mixtures.
Measurements were made under various conditions of the stress relaxation (SR) and elastic recovery (ER) of mixtures of paracetamol and microcrystalline cellulose (Avicel) and of the tensile strengths (T) of their tablets. T was inversely proportional to ER/SR. Tablets laminated or capped when they contained less than 25% w/w of cellulose and the value of ER/SR measured at 20 kN over a compression/decompression/ejection cycle of 2 min, was greater than 9. Addition of between 2 and 4% w/w of water increased the tensile strengths of tablets, provided they contained less than 75% w/w of cellulose, but more water caused decreases in T. Additions of up to 10% w/w stearic acid also caused decreases in T. Explanations are provided for the results.
Acetaminophen↗
Protein 4.1 is involved in a structural thermotropic transition of the red blood cell membrane detected by a spin-labeled stearic acid.
Proteins involved in a structural transition in red blood cell membranes detected at 8 +/- 1.5 degrees C by a stearic acid spin-label have been investigated. Calcium loading of red blood cells with ionophore A23187 caused the disappearance of the 8 degrees C transition. Protein 4.1 appears to be the most susceptible protein to Ca2+ treatment. Antibodies specific for spectrin, band 3 (43K cytoplasmic domain), and protein 4.1 have been utilized as specific probes to modify membrane thermotropic properties. The 8 degrees C transition was eliminated by anti-4.1 protein antibodies but was not modified by the other antibodies. To further characterize the protein(s) involved in the transition, ghosts were subjected to sequential extraction of skeletal proteins. The extraction of band 6, spectrin, and actin did not modify the 8 degrees C transition. In contrast, high-salt extraction (1 M KCl) of spectrin-actin-depleted vesicles, a procedure that extracts proteins 2.1 and 4.1, was able to eliminate the 8 degrees C transition. Rebinding of purified protein 4.1 to the high salt extracted vesicles restored the 8 degrees C transition. These results indicate the involvement of protein 4.1 in the transition and suggest a functional membrane association of this protein. The binding of protein 4.1 to the membrane seems to contribute significantly to the thermotropic properties of red blood cells.
Antibodies↗
Improved performance of preordered fungal protease-stearic acid biocomposites: enhanced catalytic activity, reusability, and temporal stability.
In an earlier report on fungal protease (F-prot)-fatty acid biocomposite film formation [Gole et al. Anal. Chem. 2000, 72, 4301], it was observed that the biocatalytic activity of the immobilized enzyme was comparable to that of the free enzyme in solution. However, a somewhat negative aspect of the protocol was the steady loss in activity during reuse and storage of the biocomposite film. In this paper, we address the latter issues and demonstrate successful attempts toward the realization of efficient biocomposite films with enhanced biological activity, temporal stability, and excellent reusability. The improved performance of the F-prot-stearic acid biocomposite is accomplished by preordering the fatty acid film by incorporation of Pb(2+) ions into the lipid matrix prior to enzyme immobilization. The lead cation induces lamellar ordering in the lipid film and thus facilitates diffusion of the F-prot molecules into the lipid matrix and accessibility of the substrate molecules (hemoglobin, Hb) to the entrapped F-prot enzyme molecules. The preordering consequently leads to effective control of the "mass transport" problem and might be responsible for the enhanced biological activity ( approximately 36%) of the enzyme molecules in the biocomposite in comparison with the free enzyme in solution, as well the excellent reusability of the composite film. In addition to biocatalytic activity measurements, the formation and characterization of the F-prot-lead stearate biocomposite films was done by quartz crystal microgravimetry and X-ray diffraction.
Catalysis↗