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PubMed1979

Conductivity and hardness changes in aged compacts.

Batches of sodium, potassium, and ammonium chloride tablets containing no excipients and spray-dried lactose tablets containing 0.5% magnesium stearate were stored at 20 and 76% relative humidity. Electrical resistance and hardness measurements were made within 1 hr after compression and at intervals during a 45-day period. Hardness values of sodium, potassium, and ammonium chloride tablets stored at 20% relative humidity increased from 70 to 200% at 45 days, while conductances decreased 10-fold. Tablets stored at 76% relative humidity showed no increases or slight decreases in hardness with slight increases in conductance. Lactose tablets decreased slightly in hardness with corresponding increases in conductance.

Ammonium Chloride↗
PubMed1981

Free fatty acid-induced platelet aggregation: studies with solubilized and nonsolubilized fatty acids.

The aggregation response of washed porcine platelets to the sodium salts of stearic, oleic, palmitic, and myristic acids was analyzed turbidometrically. The fatty acids were prepared as aqueous suspensions and as taurocholate- or albumin-solubilized systems. The final concentration of fatty acid in the platelet preparation varied between 70 and 600 microM. This range was within or below the normal physiological limits of 300-1200 microM. Platelet aggregation was observed with both the suspended and taurocholate-solubilized fatty acids. The extent of platelet aggregate formation increased with the fatty acid concentration and chain length. With the exception of stearate, the taurocholate-solubilized fatty acids were more active than the suspensions. Albumin-solubilized fatty acids were devoid of platelet aggregating activity. Particle-size analysis of the solubilized fatty acids indicated that fatty acid precipitation had occurred subsequent to the addition of taurocholate-solubilized fatty acids to the platelets. This precipitation did not occur with the albumin-solubilized systems, suggesting that the fatty acids must assume a particulate physical state to induce aggregation. Platelet aggregation induced by fatty acids was not inhibited by 80 nM epoprostenol, 75 microM alprostadil, or 150 microM indomethacin. This finding indicated that the fatty acid-induced platelet aggregation was independent of cyclic AMP-related calcium shift, cyclooxygenase-arachidonate, or granular nucleotide release mechanisms.

Adenosine Diphosphate↗
PubMed1983

Solid dispersions of testosterone with reduced presystemic inactivation.

Dissolution rates of solid dispersions of testosterone in various lipids or polyethylene glycol 6000 with and without surfactants were determined. In a limited study, selected dispersions were evaluated for oral absorption efficiency in a 32-year-old male. Significant reductions in urinary testosterone metabolites to testosterone ratios were observed with a 1:4 weight ratio of testosterone-polyethylene glycol 6000 and a 1:4:0.25 weight ratio of testosterone-cholesteryl stearate-sorbitan monolaurate.

Adult↗
PubMed1985

Determination of erythromycin in serum and urine by high-performance liquid chromatography with ultraviolet detection.

A high-performance liquid chromatographic analysis of erythromycin in human serum and urine with UV detection at 200 nm is presented. The method involves a solid-phase extraction procedure followed by a simple phase separation step and chromatography on a reversed-phase column. The method has sensitivity limits of 0.25 and 1.0 micrograms/mL in serum and urine, respectively, and is sufficiently sensitive to monitor concentrations of erythromycin in human serum and urine after the administration of a single 500-mg erythromycin stearate tablet.

Chromatography, High Pressure Liquid↗
PubMed1986

An investigation of some factors influencing plug formation and fill weight in a dosing disk-type automatic capsule-filling machine.

The progressive formation of plugs resulting from successive tamps in a dosing disk-type automatic capsule-filling machine was investigated for three fillers: anhydrous lactose, dicalcium phosphate, and microcrystalline cellulose. An evaluation of seven compaction parameters revealed that all tamping stations and all piston positions within a station, with the exception of station #1, contribute equally to plug formation. Model calculations suggesting that fill weight could be achieved in only three tamps were supported by direct experimental observation. The effective available fill volume was shown to be greater than the nominal volume of the dosing disk cavity. This was verified by using a modified scrape-off at station #5, which eliminated the powder head over the disk at that station. Here, increases in tamping force resulted in harder plugs, as measured with an improved plug mechanical strength tester, with fill weights remaining unchanged. However, plug segments did not increase in mechanical strength when additional segments were compressed over them using the same force. For one excipient (microcrystalline cellulose), the fill weights and the mechanical strengths of systems containing 0, 0.10, 0.25, and 0.50% magnesium stearate were measured. The 0.10% level was found to be optimum in that it resulted in maximum plug mechanical strengths and fill weights, regardless of the number of tamps used and/or their intensity.

Capsules↗
PubMed1991

Design and evaluation of sustained-release tablets of lithium in a fat matrix and its bioavailability in humans.

The development of sustained-release lithium (Li) tablets, intended to release the active principle at a rate of 1.0 mM/h for 10 h, was undertaken. The parameters used for the control of the release were the glyceril palmite-stearate content, the carboxypolymethylene content, and the compression force. The experimental design is based on Hadamard's matrices and is of the adaption by stages type. The formulation seen as optimal from in vitro assays was later assessed in vivo by a crossover study of six subjects. The parameters used to measure the bioavailability were the total amount of Li excreted in the urine in the 96 h following ingestion, the maximum urinary excretion rate, and the time at which this rate was reached. The acceptability interval for the first two parameters was established from the theoretical curve of urinary excretion, which was calculated by convolution of the desired in vivo release variable (1.0 mM/h for 10 h) by the absorption-disposition variable obtained after administering the preparation in Li carbonate capsules. The results obtained show that the bioavailability of the formulation is 75% of the immediate-release formulation used as control and that the release rate, although close to the desired value, lasts only 7 or 8 h; these results agree with those given by numerical deconvolution using the mean urinary excretion curves.

Acrylic Resins↗
PubMed1994

Thermodynamic analysis of energy dissipation by pharmaceutical tablets during stress unloading.

A thermodynamic analysis of the energy transformations occurring within pharmaceutical tablets during the unloading phase of compaction was performed on Avicel, calcium phosphate, acetaminophen, and calcium oxalate. This analysis was based on viscoelastic stress data collected using an instrumented rotary press and was conducted for the purpose of determining the extent and nature of energy release, beyond that of force displacement, during this phase of compaction. The four materials investigated were selected to reflect a range of compaction properties, and the viscous vs force-displacement energy distributions were seen to be consistent with their brittle vs plastic character. Magnesium stearate, added in various concentrations up to 4% w/w, was found to act both as an internal lubricant for particle-particle slipping and as a moderator of interparticulate bonding.

Acetaminophen↗
PubMed1995

Drug release from compressed hydrophilic POLYOX-WSR tablets.

Drug release from compressed tablets manufactured with a powder mixture of poly(ethylene oxide) (PEO), a drug, and magnesium stearate is presented. Several factors such as molecular weight, drug loading, drug solubility, the pH of the dissolution medium, and stirring rate are investigated. The drug release from the high molecular weight PEO tablets (MW = 2 x 10(6) and 4 x 10(6)) is governed by the swelling of the polymer rather than by the erosion of the polymer, leading to anomalous release kinetics. However, the drug release from the low molecular weight PEO (MW = 0.9 x 10(6)) is controlled primarily by the swelling/erosion of the polymer, resulting in front synchronization and a constant release rate. It is observed that drug loading and drug solubility do not influence the release of drugs from low molecular weight PEO tablets. The pH of the dissolution medium and the stirring rate do not affect the drug release regardless of the molecular weight of the PEO.

Chemistry, Pharmaceutical↗
PubMed2004

Rapid PKA-catalysed phosphorylation of boar sperm proteins induced by the capacitating agent bicarbonate.

In boar spermatozoa, the capacitating agent bicarbonate has been shown to induce rapid changes both in plasma membrane lipid architecture and in motility; in each case, a PKA-dependent pathway is involved. Early bicarbonate-induced changes in protein phosphorylation were probed using a commercial antibody against the phosphorylated form of the consensus substrate site for cyclic AMP-dependent protein kinase. The antibody detected relatively few bands in sperm extracts, of which only a small number showed incubation-dependent changes. While the quantitative response varied between boar ejaculates, in general terms bicarbonate induced phosphorylation increases in bands of 96, 64, and 59 kDa within 80 sec. The changes reached a maximum after about 160 sec, declined somewhat thereafter, and then increased again slowly as incubation progressed further (up to 21 min). The bicarbonate-induced increases were strongly dependent on the presence of BSA in the incubation medium. They were inhibited by H89 (PKA inhibitor) but not by GF (PKC inhibitor), and were enhanced by papaverine (phosphodiesterase inhibitor) and by calyculin (protein phosphatase inhibitor). The cyclic AMP analogue cBIMPS was able to mimic bicarbonate action though its effect was less dramatic. Stearated Ht31, a permeable inhibitor of PKA's binding to A-kinase anchoring protein, did not affect either the intensity or the specificity of the bicarbonate-induced phosphorylation changes, though it blocked motility entirely. Immunocytochemical studies revealed marked bicarbonate-dependent phosphorylation changes in the post-acrosomal region of the head and in the neck, midpiece, and anterior regions of the tail. Fractionation of stimulated spermatozoa showed that all bands detectable with the antibody were bound to heads and to midpieces and associated large tail fragments; no bands were detected in either small tail or membrane fragments or in the cytoplasmic fraction. Differential extraction of the midpiece/large tail fraction revealed two protein bands with closely similar electrophoretic mobilities to the 96- and 59-kDa phosphorylated bands; MALDI-TOF analyses of these bands revealed both to be members of the Odf2 family.

Animals↗
PubMed1988

Modulation of water proton relaxation rates by liposomes containing paramagnetic materials.

Liposomes containing paramagnetic chemicals have significant potential for enhancing the effectiveness and selectivity of contrast agents in magnetic resonance imaging. We have studied the interactions of water, liposomes, and contrast agents using NMR and ESR. We find that the permeability of liposomes to water is of major importance in determining the effects of these systems on water proton relaxation. Key factors include (1) liposome composition, which determines the phospholipid membrane phase behavior as a function of temperature; (2) liposome structure (unilamellar or multilamellar); (3) location of the contrast agent in the liposome (aqueous space or lipid membrane); and (4) binding of contrast agents by liposomes. By appropriate selection of these factors it is possible to obtain effective proton relaxation enhancement in a manner suitable for particular experimental or clinical needs for contrast in MRI. For maximum relaxivity using lipophilic nitroxides, the optimum system appears to be 5-doxyl stearate in multilamellar vesicles with a membrane composition that gives a phase transition temperature slightly above body temperature.

Contrast Media↗
PubMed2002

Myosin light chain phosphorylation and growth cone motility.

According to the treadmill hypothesis, the rate of growth cone advance depends upon the difference between the rates of protrusion (powered by actin polymerization at the leading edge) and retrograde F-actin flow, powered by activated myosin. Myosin II, a strong candidate for powering the retrograde flow, is activated by myosin light chain (MLC) phosphorylation. Earlier results showing that pharmacological inhibition of myosin light chain kinase (MLCK) causes growth cone collapse with loss of F-actin-based structures are seemingly inconsistent with the treadmill hypothesis, which predicts faster growth cone advance. These experiments re-examine this issue using an inhibitory pseudosubstrate peptide taken from the MLCK sequence and coupled to the fatty acid stearate to allow it to cross the membrane. At 5-25 microM, the peptide completely collapsed growth cones from goldfish retina with a progressive loss of lamellipodia and then filopodia, as seen with pharmacological inhibitors, but fully reversible. Lower concentrations (2.5 microM) both simplified the growth cone (fewer filopodia) and caused faster advance, doubling growth rates for many axons (51-102 microm/h; p <.025). Rhodamine-phalloidin staining showed reduced F-actin content in the faster growing growth cones, and marked reductions in collapsed ones. At higher concentrations, there was a transient advance of individual filopodia before collapse (also seen with the general myosin inhibitor, butanedione monoxime, which did not accelerate growth). The rho/rho kinase pathway modulates MLC dephosphorylation by myosin-bound protein phosphatase 1 (MPP1), and manipulations of MPP1 also altered motility. Lysophosphatidic acid (10 microM), which causes inhibition of MPP1 to accumulate activated myosin II, caused a contracted collapse (vs. that due to loss of F-actin) but was ineffective after treatment with low doses of peptide, demonstrating that the peptide acts via MLC phosphorylation. Inhibiting rho kinase with Y27632 (100 microM) to disinhibit the phosphatase increased the growth rate like the MLCK peptide, as expected. These results suggest that: varying the level of MLCK activity inversely affects the rate of growth cone advance, consistent with the treadmill hypothesis and myosin II powering of retrograde F-actin flow; MLCK activity in growth cones, as in fibroblasts, contributes strongly to controlling the amount of F-actin; and the phosphatase is already highly active in these cultures, because rho kinase inhibition produces much smaller effects on growth than does MLCK inhibition.

Actins↗
PubMed1990

Fragment pathway analysis using automated tandem mass spectrometry on an ion-trap mass spectrometer.

A "key-sequence" procedure is presented for the automated tandem mass spectrometric analysis of compounds on a Finnigan ion-trap mass spectrometer. This allows fragmentation pathways of a range of masses or even a complete spectrum to be prepared automatically, obviating the tiresome preparation and optimization of individual scan-editor files. The procedure is limited by the speed of the driving computer; an "IBM-AT", for example, permits more than 10 mass units to be scanned per minute. It is calibrated with perfluorotributylamine and methyl stearate is used to demonstrate its results. The Finnigan ion-trap "programming option" is necessary for implementation of the procedure.

Mass Spectrometry↗
PubMed2001

Supersonic gas chromatography/mass spectrometry.

A new gas chromatography/mass spectrometry (GC/MS) system was designed and evaluated which we have named 'Supersonic GC/MS'. It is based on a modification of a commercially available GC/MS system to include a supersonic molecular beam (SMB) MS interface. In this system the standard electron ionization (EI) ion source was replaced with a fly-through EI ion source mounted in the path of the SMB. A hyperthermal surface ionization (HSI) ion source combined with a 90 degrees ion mirror (for the EI-produced ions) was also added, and placed inside the quadrupole mass analyzer in place of its original EI ion source. The 'Supersonic GC/MS' system requires 18 cm added bench space plus the addition of an air-cooled 60 L/s diffusion pump and a 537 L/min rotary pump. The system is user friendly since all the gas flow rates, heated zones, sampling and data analysis are performed the same way as the original system and are computer-controlled via the original software. Similar EI sensitivity was obtained as with the original system for hexachlorobenzene and octafluoronaphthalene, while improved EI detection limits were demonstrated for methyl stearate and eicosane due to the significant enhancement of their molecular ion abundances. A GC/MS detection limit of 500 ag for pyrene was demonstrated using HSI. Good supersonic expansion cooling was achieved with large alkanes, despite the use of a rotary pump at the nozzle chamber instead of a diffusion pump. High temperature GC/MS analysis was demonstrated for large polycyclic aromatic hydrocarbons (PAHs) including ovalene and decacyclene (ten rings). Library searches with EI mass spectra are demonstrated, and it is explained why the enhancement of the molecular ion actually improves the library search in most cases. The analysis of large phthalate esters is also described, and the improvement obtained is shown to originate from their enhanced molecular and high mass fragment ions.

Environmental Pollutants↗
PubMed1993

N-acylphosphatidylethanolamine synthesis in plants: occurrence, molecular composition, and phospholipid origin.

We have identified a microsomal phospholipid as N-acylphosphatidylethanolamine (NAPE) that was radiolabeled following incubation of 1-day-old cotyledons of cotton seedlings with [14C]ethanolamine. Radiolabeled NAPE comigrated with commercially available L-alpha-dipalmitoyl phosphatidyl(N-palmitoyl)ethanolamine (std-NAPE) in one- and two-dimensional TLC. This NAPE comprised 7.2 +/- 1.0% (by weight) of microsomal phospholipids when hot isopropanol was used to inactivate endogenous phospholipases prior to extraction of lipids. In vitro degradation of putative cottonseed radiolabeled NAPE by Streptomyces chromofuscus phospholipase D resulted in production of a ninhydrin-reactive, radiolabeled lipid which comigrated with N-acylethanolamine (NAE) that was produced from a similar enzymatic cleavage of std-NAPE. Transmethylation of cottonseed radiolabeled NAE yielded radiolabeled ethanolamine and fatty acid methyl esters, nearly all of which were saturated (myristate, palmitate, and stearate together were 92% of the acyl components of cottonseed NAE). Positional analysis and relative abundance of the O-acyl groups of cottonseed microsomal NAPE were determined following a double enzymatic cleavage with Trimeresurus flavoviridis venom (phospholipase A2 activity) and S. chromofuscus phospholipase D. We substantiated our identification of cottonseed NAPE by 1H NMR spectroscopy and by mass spectrometry (fast-atom-bombardment ionization and tandem MS, FAB-MS/MS). Radiolabeled NAPE was synthesized in vivo in varying amounts from [14C]ethanolamine applied to maturing seeds of cotton and soybean, cotyledons of dark-grown cotton and soybean seedlings, cotyledons of light-grown okra, cotton and soybean seedlings, endosperm tissue of castor bean, and suspension cell cultures of rice. In pulse-chase radiolabeling experiments in cotyledons of 1-day-old cotton seedlings, radiolabeled NAPE increased and radiolabeled phosphatidylethanolamine (PE) decreased over a 12-h chase period (in the dark or light), suggesting that NAPE was synthesized from PE in vivo. In vitro, the synthesis of NAPE from PE (radiolabeled in vivo) proceeded in a linear fashion in microsomes of cotton cotyledons with or without 1 mM EGTA and with or without 1 mM CaCl2 for 90 min. NAPE was synthesized in vitro from PE synthesized by the exchange pathway (microsomes preincubated with [14C]++e+thanolamine) and from PE synthesized by the nucleotide pathway (microsomes preincubated with [14C]CDPethanolamine). Collectively, our data indicate that (a) NAPE is a widespread, natural phospholipid component of plants, (b) NAPE is synthesized in vivo under normal physiological growth conditions in cotyledons of cotton seedlings, (c) NAPE is localized and synthesized in cottonseed microsomes, and (d) NAPE is likely synthesized by a direct acylation of PE.

Acylation↗
PubMed1994

Sequential oxygenation of linoleic acid in the fungus Gaeumannomyces graminis: stereochemistry of dioxygenase and hydroperoxide isomerase reactions.

Linoleic acid is sequentially oxygenated to (7S,8S)-dihydroxylinoleic acid by dioxygenase and hydroperoxide isomerase activities present in the fungus Gaeumannomyces graminis (Brodowsky, I. D., Hamberg, M., and Oliw, E. H., J. Biol. Chem. 267, 14738-14745 (1992)). Linoleic acids stereospecifically deuterated at C-7 and C-8 were prepared by biological desaturation of the corresponding stearates and used to determine the stereochemistry of the hydrogen abstractions occurring in the dioxygenase- and hydroperoxide isomerase-catalyzed reactions. The dioxygenase reaction was found to involve stereospecific abstraction of the pro-S hydrogen from C-8 followed by antarafacial insertion of dioxygen to produce (8R)-hydroperoxylinoleic acid. The hydroperoxide isomerase reaction consisted of conversion of (8R)-hydroperoxylinoleic acid into (7S,8S)-dihydroxylinoleic acid by stereospecific elimination of the pro-S hydrogen from C-7 and intramolecular suprafacial insertion of oxygen at C-7. Accordingly, during the conversion of linoleic acid into (8R)-hydroperoxylinoleic acid, the absolute configuration of C-8 was inverted, while the conversion of (8R)-hydroperoxylinoleic acid into (7S,8S)-dihydroxylinoleic acid occurred with retention of absolute configuration at C-7.

Deuterium↗
PubMed1994

A glycoprotein binding retinoids and fatty acids is present in Drosophila.

In the search for a possible Drosophila melanogaster homolog of interphotoreceptor retinoid-binding protein (IRBP), a approximately 140-kDa retinoid- and fatty acid-binding glycoprotein found in vertebrates, the 110,000 g supernatant fraction prepared from homogenates of fly heads was analyzed for the presence of proteins capable of binding radiolabeled retinol and palmitic acid. A soluble protein, which binds concanavalin A and has a retention time on size-exclusion high-performance liquid chromatography identical to that of purified bovine IRBP, was identified as binding both ligands. As assessed by fluorescence titration, the protein fraction obtained by concanavalin A-Sepharose affinity chromatography and size-exclusion chromatography of fly head supernatant had apparent dissociation constants of 2.9 x 10(-7) +/- 0.6 M for all-trans retinol, with the number (n) of independent ligand binding sites per protein molecule = 2, and 3.5 x 10(-7) +/- 0.1 M for 16-[9-anthroyloxy] palmitic acid with n = 7. High-performance liquid chromatography of hexane extracts of this protein fraction resolved several peaks with polarity and relative retention times similar, but not identical to all-trans retinol and retinal and their 9-, 11-, and 13-cis isomers. Gas chromatography/mass spectrometry analysis of fatty acid methyl esters prepared following lipid extraction of the protein identified lauric, myristic, palmitic, palmitoleic, and oleic acids as being covalently bound. Laurate, myristate, palmitate, and stearate were noncovalently bound. The apparent molecular mass of the Drosophila protein as assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and silver staining of the retinoid- and fatty acid-binding peak obtained by hydrophobic interaction chromatography of the size-exclusion fraction was approximately 70 kDa.

Animals↗
PubMed1996

Effects of fumonisin B1 and (hydrolyzed) fumonisin backbone AP1 on membranes: a spin-label study.

Electron spin resonance (ESR) spectroscopy and spin label techniques have been used to study the effects of fumonisin B1 (FB1) and hydrolyzed fumonisin backbone (AP1) on the structural and dynamic properties of phosphatidylcholine membranes at the molecular level. Multilamellar liposomes consisting of dimyristoylphosphatidylcholine (DMPC) and egg yolk phosphatidylcholine (EYPC) were used. Six different nitroxide spin labels were used to determine what effects FB1 may impart on the ordering and mobility of lipids in membranes. The experimental results disclose the following: (1) In the fluid phase membrane, FB1 significantly increases the fluidities of n-doxylstearic acid (SA) spin labels (SL) attached to carbons 5 and 7, which disorders the alkyl chains and perturbs the surface region of the bilayer; by comparison, minimal effects were detected near the center of the bilayer. (2) In the gel phase, FB1 and AP1 imparts marked rigidifying effects on membrane fluidity, which enlarges the change in ordering on the phase transition even further. (3) FB1 also restricts the mobility of the (rigid) cholestane spin label. (4) A reduction in mobility of the tempo-stearate spin label suggests that the tricarballylic acid (TCA) moieties of FB1 might mimic the structure of polar headgroups in phospholipids. The present results may provide additional mechanisms to elucidate the toxicological activities of the fumonisins.

Dimyristoylphosphatidylcholine↗