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PubMed1992

Percutaneous absorption of ketoprofen from acrylic gel patches containing d-limonene and ethanol as absorption enhancers.

The percutaneous absorption of ketoprofen (KPF) from gel patches containing d-limonene and ethanol was investigated in rats. Plasma levels of KPF varied with the kind of polymers which constitute the gel patch, and the highest level was observed when the copolymer of ethylacrylate (EA) and diethyleneglycolmethacrylate (DEGMA) was used as a vehicle. The amount of KPF permeating through the rat skin from the gel patch was well correlated with that of ethanol. Permeations were enhanced with increase in the amount of d-limonene distributed from the vehicle to the skin tissue. The amount of d-limonene accumulated in the skin varied greatly with the kind of polymers; the highest accumulation was observed with the EA-DEGMA copolymer, and decreased with increasing affinity of d-limonene to the polymers. The reason EA-DEGMA copolymer showed the highest percutaneous absorption of KPF from gel patches containing d-limonene may be the hydrophilic nature of this polymer which showed the lowest affinity to d-limonene.

Administration, Cutaneous↗
PubMed2006

Limitations arising from two-photon absorption of solvent in pulsed-laser thermal lens detection: determination of the two-photon absorption coefficient of ethanol at 266 nm.

Two-photon absorption of the solvent under pulsed-laser excitation at 266 nm produces a high background thermal lens signal interfering with the analyte signal. Discrimination of both solvent and analyte signals along with calibration of the photothermal response has allowed the determination of the two-photon absorption coefficient of ethanol. The obtained value, 3.0x10(-10) cm W-1, is close to the literature values obtained from transmittance measurements using picosecond or femtosecond laser pulses.

Absorption↗
PubMed2005

Absorption of myo-inositol hexakisphosphate (InsP6) through the skin: study of the matrix effects. mechanism of phytate topical absorption.

Myo-inositol hexakisphosphate (InsP6, phytate) is a molecule to which diverse beneficial properties have been attributed. Some of these properties are related to its dermatological use as discolouring agent, on preventing calcinosis cutis or due to its important role on premature aging. Other studies also seem to demonstrate a capacity of InsP6 to inhibit skin cancer. In this paper, the effect of the vehicle of topical administration of phytate is studied, using four groups of male Wistar rats (n = 6) fed with an InsP6 defficient diet and treated with a hydrophyl gel or an O/W moisturizing cream with two different concentrations of InsP6. Due to the correlation between InsP6 absorption and its urinary excretion, these last values were used to evaluate this process. It was found that phytate was absorbed through the skin using both a gel or a cream, demonstrating that its absorption is independent on the matrix used for topical treatment. However, urinary InsP6 values were slightly higher when using the gel, but in all cases values were much higher than those found with oral InsP6 treatment, due to the formation of insoluble species in the gastrointestinal tract when InsP6 is administered orally.

Administration, Topical↗
PubMedDate not supplied

Absorption of amino acids in different parts of the small intestine in growing pigs. II. Effect of addition of certain amino acids on absorption of different amino acids from acid hydrolysed casein.

The study was carried out on pigs weighing 50 to 60 kg with temporarily isolated loops of the upper and the distal halves of the small intestine. Isolated segments 90 to 180 cm long were perfused at a rate of 720 ml/h with solutions of acid casein hydrolysate to which 100 to 300 per cent of the original contents of some amino acids was added. The changes of amino acid composition of the solution used for perfusion influenced to a large extent of the absorption of different amino acids. Leucine, methionine and arginine, the amino acids with the greatest affinity to the transport mechanism, were most active in inhibiting the absorption of the other amino acids from the small intestine.

Amino Acids↗
PubMed1981

Drug absorption: a practical method to estimate the absorption rate constant.

A simple equation is proposed to estimate the apparent absorption rate constant (Ka). In order to test this equation, experimental data were obtained following the oral administration of 10 mg/kg of sulfamethazine (SMZ) to ten normal volunteers. The Ka was estimated in three ways (by the proposed equation, by the method of residuals and by the method of the percent unabsorbed versus time plots), and then compared to the value obtained using a NONLIN computer program. The validity of the calculated Ka was further tested by performing computer simulations and estimating the quality of the fit by comparing the coefficient of regression. It was concluded that with the proposed relationship, the estimated values of Ka are closer to the results obtained with the NONLIN method than are the Ka values calculated with graphical methods. Moreover, the calculated method has the advantage that the accuracy of the estimated Ka is not affected by fast absorption, as long as a plasma concentration prior to the peak is known and that the relationship is easy and practical to handle. The one limitation to the proposed method is that it can only be applied to drugs distributed into a single compartment.

Adult↗
PubMed1995

Ocular absorption, distribution, and systemic absorption of a novel antiglaucoma medication, prostaglandin derivative, in male white rabbits.

A prostaglandin derivative, (5Z,9 alpha,11 alpha,13E)-9,11-dihydroxyprosta- 5,13-dienoic acid sodium salt (S-1033), that lowers intraocular pressure with little adverse effect, may have clinical value in the treatment of glaucoma. After [14C]S-1033 (0.2% solution) was instilled into the eye of a white rabbit, radioactivity and S-1033 appeared in systemic plasma so rapidly (tmax, 5 min) and S-1033 was eliminated very rapidly with half-lives of 2.8 and 11.0 min at alpha- and beta-phases, respectively. The metabolite, M-1, [1R-[1 alpha,2 beta-(1E),3 alpha,5 alpha]]-3,5-dihydroxy-2-(1- octenyl)-cyclopentanepropanoic acid (tetranor-S-1033), appeared in plasma very rapidly (tmax, 5 min), suggesting that a fast metabolism was a major factor in the rapid elimination of S-1033 from plasma. The values for the ratios of the area under the curve of ocular instillation to intravenous administration for radioactivity and S-1033 were 1.01 and 0.52, respectively, indicating that more than half of the S-1033 instilled was transported into the systemic circulation. To clarify the contributing pathway of the massive and rapid systemic absorption of S-1033 after topical dosing, plasma levels of S-1033 were investigated after instillation to rabbits in which the nasolacrimal ducts were occluded. Plasma concentrations of S-1033 were slightly higher than those in intact rabbits, suggesting that conjunctiva would be as important as nasal mucosae for the systemic absorption under the physiological condition. As for the intraocular distribution, the highest levels of radioactivity were found in the cornea, conjunctiva, and anterior sclera.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗
PubMed1990

Pharmacokinetics of pafenolol in the rat: a suitable model for studying absorption mechanisms of a drug exhibiting unusual absorption properties in man.

The pharmacokinetics of pafenolol, a highly selective beta 1-adrenoceptor antagonist, have been studied in starved and unstarved rats. Separate groups received intravenous doses (0.3 and 3.0 mumol kg-1) and oral doses (1 and 25 mumol kg-1). The systemic clearance of pafenolol was constant in the dose range investigated where the absolute oral bioavailability increased from 15 to 27 per cent in the starved and from 9.1 to 21 per cent in the unstarved rats, when the oral dose was raised from 1 to 25 mumol kg-1. The blood concentration profile after an oral solution of pafenolol exhibited two peaks in the majority of the rats. The major part of the absorption was associated with the second peak which appeared about 4 h after dosing in both starved and unstarved rats. Food lowered the degree of bioavailability and shifted the tmax1 to about 1 hour compared to half an hour in starved rats. The low bioavailability was primarily due to incomplete uptake from the gastrointestinal tract. Our study shows that pafenolol is absorbed in a similar way to that in man. The mechanisms behind the dose-dependent bioavailability and the two peaks in the absorption profile after an oral solution will be further explained in the rat.

Adrenergic beta-Antagonists↗
PubMed1997

Accurate universal parameterization of absorption cross sections II--neutron absorption cross sections.

A recent parameterization (here after referred as paper I, Ref. [4]) of absorption cross sections for any system of charged ions collisions including proton -nucleus collisions, is extended for neutron-nucleus collisions valid from approximately 1 MeV to a few GeV, thus providing a comprehensive picture of absorption cross sections for any system of collision pair (charged and/or uncharged). The parameters are associated with the physics of the problem. At lower energies, the optical potential at the surface is important and the Pauli operator plays an increasingly important role at intermediate energies. The agreement between the calculated and experimental data is better than earlier published results.

Elementary Particle Interactions↗
PubMed1988

Solute absorption from the airways of the isolated rat lung. I. The use of absorption data to quantify drug dissolution or release in the respiratory tract.

Coprecipitates of fluorescein and magnesium hydroxide demonstrate delayed absorption relative to fluorescein solutions when administered to the airways of the isolated perfused rat lung (IPRL). Perfusate concentration vs time profiles showed that dissolution and not epithelial permeability was the rate-controlling factor in the airway-to-perfusate transfer process. A simple data deconvolution method was developed to determine the fluorescein release from the microparticulate coprecipitates in the airways. The deconvolution technique is generally applicable and provides values for undissolved solute remaining in the airways as a function of time provided that (a) significant binding and/or metabolism does not occur, (b) absorption from solution is apparent first order, and (c) all solid or dissolved material reaching perfused regions is absorbed within the lifetime of the preparation. Increased release rates of fluorescein occurred from precipitates containing greater starting concentrations of the dye. Dissolution profiles were similar to those that occur for log-normally distributed powders. The analysis of two unusual time profiles implied that the regional distribution of solid and dissolved material, between perfused areas and nonperfused areas, could be nonhomogeneous despite the use of a standardized dosing technique. The studies describe a method of using the IPRL with the potential to screen aerosol formulations for extended dissolution in the respiratory tract.

Aerosols↗
PubMed2001

Separation and preconcentration of chromium species by selective absorption on Lemna minor and determination by slurry atomisation electrothermal atomic absorption spectrometry.

A novel method for the separation and preconcentration of Cr(III)/Cr(VI) with Lemna minor and determination by slurry atomization electrothermal atomic absorption spectrometry (ETAAS) was developed. A sample solution was added to a polyethylene beaker containing 10 mg of 160 mesh pre-treated Lemna minor, adjusted to pH 1.0, stirred for 8 min for selective absorption of Cr(III) and then centrifuged. The upper layer of solution was transferred into another polyethylene beaker containing 10 mg of 160 mesh pre-treated Lemna minor, adjusted to pH 5.0, stirred for 12 min for adsorption of the residual Cr(VI) and centrifuged. The two residues in two centrifuge tubes were washed twice with water, 2 ml of agar solution added, stirred for 2 min, then two slurries were prepared and used for the determination of Cr(III) and Cr(VI) by ETAAS. Detection limits (3sigma) of 0.01 microg L(-1) for Cr(III) and 0.03 microg L(-1) for Cr(VI) were obtained. The relative standard deviation was 2.8% for Cr(III) and 3.3% for Cr(VI) at the 1 microg L(-1) level. The method was applied to the determination of Cr(III)/Cr(VI) in water samples. The analytical recoveries of Cr(III) and Cr(VI) added to samples were 97-102 and 96-103%, respectively.

Journal Article↗
PubMed2000

Thomson Thick X-Ray Absorption in a Broad Absorption Line Quasar, PG 0946+301.

We present a deep ASCA observation of a broad absorption line quasar (BALQSO) PG 0946+301. The source was clearly detected in one of the gas imaging spectrometers, but not in any other detector. If BALQSOs have intrinsic X-ray spectra similar to normal radio-quiet quasars, our observations imply that there is Thomson thick X-ray absorption (NH greater, similar1024 cm-2) toward PG 0946+301. This is the largest column density estimated so far toward a BALQSO. The absorber must be at least partially ionized and may be responsible for attenuation in the optical and UV. If the Thomson optical depth toward BALQSOs is close to 1, as inferred here, then spectroscopy in hard X-rays with large telescopes like XMM would be feasible.

Journal Article↗
PubMed1981

Absorption spectrum of allophycocyanin isolated from Anabaena cylindrica: variation of the absorption spectrum induced by changes of the physico-chemical environment.

The absorption spectrum of allophycocyanin of Anabaena cylindrica was studied. The extinctions of the main absorption bands (650 and 620 nm) varied depending on the protein concentration, ionic strength, and pH. At higher protein concentrations or higher ionic strength, the 650 nm band became stronger and the 620 nm band became weaker. At pH values lower than 6.0, reverse changes occurred in association with protein dissociation into monomer. Similar spectral variation was also induced by sugars and polyols. Glucose, sucrose, or glycerol (1-5 M) induced an increase in the 650 nm band and a decrease in the 620 nm band without causing any changes in protein conformation. Propylene glycol and ethylene glycol showed a reverse effect and caused protein dissociation into monomer. The difference spectra of all spectral changes were identical, consisting of a sharp and strong peak at 650 nm and a broad and weak one in the reverse direction at a wavelength below 620 nm. The spectral variation probably results from shifts of the electronic state of phycocyanobilin. We postulated that a protein field favorable to the state producing the 650 nm band is established around phycocyanobilin when the protein takes a "tight state" through protein association or by the action of sugar in aqueous environment; in a "relaxed state" in the monomer, the state of phycocyanobilin similar to that in phycocyanin becomes dominant.

Anions↗
PubMed2005

Effectiveness of pirotiodecane, absorption enhancer, on nasal absorption in rabbits.

The absorption enhancing effect of 1-[2-(decylthio) ethyl] azacyclopentan-2-one (Pirotiodecane), on drug permeation across rabbit nasal mucosa was studied. The nasal epithelial mucosa was isolated from rabbit nasal septum and mounted in an Ussing chamber to allow for monitoring of the membrane resistance (Rm), and the permeation of fluorescein isothiocyanate-labeled dextran (FD-4, M.W. 4,400 Da). Treatment with 0.05, 0.1, and 0.2% Pirotiodecane for 60 min decreased Rm, and increased the cumulative amount of FD-4 permeated in a concentration-dependent manner, suggesting that Pirotiodecane possesses passively a disassembly of tight junction to enable the enhanced FD-4 permeation. The remarkable increase in plasma concentration of FD-4 was also observed in intranasal co-administration with 1% Pirotiodecane in rabbits. The Rm was virtually maintained after the removal of Pirotiodecane, although recovery of Rm was not seen. On the other hand, the increase in plasma concentration of FD-4 with intranasal co-administration of 1% Pirotiodecane in rabbits in vivo was not observed in FD-4 administration at 15-60 min after administration of 1% Pirotiodecane alone. It was concluded that Pirotiodecane possesses a relatively short absorption enhancing effect through nasal epithelial.

Administration, Intranasal↗
PubMed1992

Interactions of praseodymium and neodymium with nucleosides and nucleotides: absorption difference and comparative absorption spectral study.

The interactions of praseodymium(III) and neodymium(III) with nucleosides and nucleotides have been studied in different stoichiometry in water and water-DMF mixtures by employing absorption difference and comparative absorption spectrophotometry. The 4f-4f bands were analysed by linear curve analysis followed by gaussian curve analysis, and various spectral parameters were computed, using partial and multiple regression method. The magnitude of changes in both energy interaction and intensity were used to explore the degree of outer and inner sphere coordination, incidence of covalency and the extent of metal 4f-orbital involvement in chemical bonding. Crystalline complexes of the type [Ln(nucleotide)2(H2O)2]- (where nucleotide--GMP or IMP) were characterized by IR, 1H NMR, 31P NMR data. These studies indicated that the binding of the nucleotide is through phosphate oxygen in a bidentate manner and the complexes undergo substantial ionisation in aqueous medium, thereby supporting the observed weak 4f-4f bands and lower values for nephelauxetic effect (1-beta), bonding (b) and covalency (delta) parameters derived from coulombic and spin orbit interaction parameters.

Guanosine Monophosphate↗
PubMed1987

[Radiation absorption (CT) and proton relaxation times (MR) of the blood. Quantification of the effect of cell, protein, mineral and water content on total absorption].

The exact knowledge of the physical properties of the blood is of great help in image interpretation. Accumulations of liquid with different components of protein and cells must be differentiated from neoplastic tissues. The blood with its composition will influence from the imaging point of view all other blood supplied tissues. The CT number (radiation absorption) of the entire tissue is the sum of the radiation absorption of its single components. To demonstrate this we used human blood as a "tissue model". The proton-relaxation times (T1 and T2) were measured in their dependence on the red cell concentration.

Blood↗
PubMedDate not supplied

Determination of zinc in serum, blood, and ultrafiltrate fluid from patients on hemofiltration by graphite furnace/atomic absorption spectroscopy or flow injection analysis/atomic absorption spectroscopy.

Two methods were optimized for the determination of zinc in samples of blood, serum, and ultrafiltrate fluid from patients with chronic renal impairment undergoing hemofiltration. In the first procedure, after acid digestion of the samples, Zn in blood and serum is determined by a system coupled to flow injection analysis and atomic absorption spectroscopy. The method is rapid, automated, simple, needs small amounts of sample, and has acceptable analytical characteristics. The analytical characteristics obtained were as follows: determination range of method, 0.05-2.0 ppm of Zn; precision as coefficient of variation (CV), 5.3%; recovery, 95-105%; and detection limit (DL), 0.02 ppm. The second method is optimized for ultrafiltrate fluid because the sensitivity of the first procedure is not suitable for the levels of Zn (ppb or ng/mL) in these samples. The technique chosen was atomic absorption spectroscopy with electrothermal atomization in a graphite furnace. The analytical characteristics obtained were as follows: determination range of method, 0.3-2.0 ppb Zn; CV, 5.7%; recovery, 93-107%; and DL, 0.12 ppb. The methods were used to determine zinc in samples of blood, serum, and ultrafiltrate fluid from 5 patients with chronic renal impairment undergoing hemofiltration to discover whether there were significant differences in the zinc contents of blood, serum, and ultrafiltrate fluid after the hemofiltration process. An analysis of variance of the experimental data obtained from a randomly selected group of 5 patients showed that zinc concentrations in the ultrafiltrate fluid, venous blood, and venous serum do not vary during hemofiltration (p < 0.05), whereas in arterial blood and serum, the time factor has a significant effect.

Flow Injection Analysis↗
PubMed1997

Absorption and metabolism of the absorption enhancer didecanoylphosphatidylcholine in rabbit nasal epithelium in vivo.

The absorption enhancer, didecanoylphosphatidylcholine (DDPC), improves the nasal absorption of human growth hormone in rabbits. We elucidated the uptake and the metabolism of 1,2-di[1-14C]decanoyl-L-3-phosphatidylcholine and 1,2-didecanoyl-L-3-phosphatidyl[N-methyl-3H]choline in rabbit nasal mucosa in vivo. One minute after nasal application of DDPC, 4.4-7.5% of the applied dose was found absorbed into the mucosa. The retained radioactivity left the tissue in <2 hr. The lipophilic tissue extract revealed that, at t = 1 min, only 1.1-1.4% of the applied dose was found as intact DDPC in the nasal mucosa. The other labeled compounds were decanoic acid, DDPC reacylated with endogenous fatty acids, a neutral lipid, and very small amounts of lyso-DDPC and phosphatidylethanolamine. The water-soluble metabolites revealed formation of phosphorylcholine, glycerophosphorylcholine, cytidinediphosphatecholine, and a slight amount of choline. The detection of these metabolites suggests that DDPC was rapidly cleared from the nasal mucosa, partly by degradation by phospholipases. In addition, data illustrated reutilization of DDPC metabolites in the formation of cytidinediphosphatecholine and phosphatidylethanolamine, together with DDPC being reacylated with endogenous fatty acids. The rapid formation of decanoic acid raises the possibility that this acid may contribute significantly to the drug-enhancing properties of DDPC.

Administration, Intranasal↗