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PubMedDate not supplied

[Intestinal absorption of fats in children using serum turbidity and triglyceride absorption tests].

Intestinal fat absorption was studied, using serum turbidity and serum triglyceride levels, which were determined before and after a test meal of 2 g neutral fat per kg b.w. in 33 children: 25 controls, four with cystic fibrosis, and four with celiac disease. The results proved that the easy-to-perform serum turbidity test was superior to the triglyceride absorption test in characterizing fat digestion and absorption. The most substantial increase in both tests occurred about three hours after the oral fat load.

Celiac Disease↗
PubMed1984

[Function diagnosis of small intestine absorption using the modified D-xylose absorption test].

Based on a biophysical model of the absorptive system a modified D-xylose test has been inaugurated, which is well suited to comprehensively assess the process of intestinal absorption. According to the author's experience of many years the test is a well-suited method for detecting changes in intestinal absorption. It excels by its high validity and reliability. Its practical accomplishment is easy and needs no expensive equipment. The method and the processing and evaluation of the measured values are described in detail.

Adolescent↗
PubMed1976

Effect of electric fields on the absorption spectrum of dye molecules in lipid layers. V. Refined analysis of the field-indicating absorption changes in photosynthetic membranes by comparison with electrochromic measurements in vitro.

The comparison of light-induced absorption changes in photosynthesis with electrochromic spectra of the isolated pigments in vitro is renewed more thoroughly and described in detail, involving new measurements of the linear electrochromism of oriented chlorophyll beta [6]. 1. The coincidence of the maxima and minima in the in vivo spectrum with those in the in vitro superposition is better than in previous studies [4]. 2. The molar ratio of the pigments now used for the superposition of the in vitro spectra is the same as that in vivo. 3. From this and from surface-pressure/area diagrams of the chlorophylls on a water surface, conclusions are drawn concerning the preferential orientations of the dipole moment differences of the red and blue absorption bands of the bulk chlorophylls in the membrane. 4. From the comparison of the electrochromism of the carotenoids with the absorption change at 520 nm in vivo, it is concluded that the bulk of the carotenoids are oriented at a rather flat angle in the membrane (approximately 16 degrees).

Carotenoids↗
PubMed2004

Topological estimation of electronic absorption bands of arene absorption spectra as a tool for modeling their toxicity and environmental pollution.

A novel application of distance-based topological indices : Wiener (W)-, Szeged (Sz)-, Padmakar-Ivan (PI)-, and Sadhana (Sd)-indices in modeling electronic absorption bands of arene absorption spectra has been described. It is demonstrated that all these indices correlate linearly with the logarithm of beta and para electronic absorption bands in several series of arene systems. The results have shown that our methodology is best suited for the estimation--lnlambda(beta), while comparatively less significant results are obtained in case of the estimation of lnlambda(p). The statistical analysis of the data have shown that PI index gives better results for modeling lnlambda(beta); while Sz index proved better for modeling lnlambda(p). The results are critically discussed on the basis of regression parameters and quality of correlation. Such a study will be useful as a tool for modeling toxicity of arene system as well as their environmental pollution.

Electrochemistry↗
PubMed2004

Assignment of charge transfer absorption band in optical absorption spectra of the adsorbate-silver colloid system.

In this paper we reported the UV-visible-NIR optical absorption properties of silver colloid, employed as a high efficient substrate in surface-enhanced Raman spectra (SERS), under various conditions. Experimental results revealed that the new absorption band, usually appearing in the longer wavelength region due to the addition of molecules, was related to the direct adsorption of molecules on colloidal silver surface. When the adsorption occurred, this new band would appear. Once the molecules were desorbed from silver surface, the new band could not be observed. Some evidences inferred that the new absorption band was associated with the effect of charge-transfer transition between adsorbates and colloidal silver particles, while not with the effect of the surface plasma resonance due to the silver particles aggregation which was usually attributed to in previous research work.

Colloids↗
PubMed2005

X-ray absorption fine structure combined with X-ray fluorescence spectrometry. Improvement of spectral resolution at the absorption edges of 9-29 keV.

X-ray absorption near-edge structure (XANES) suffers from core-hole lifetime broadening at a higher energy absorption edge, such as Sn K (29 keV, Gamma(K) = 8.49 eV). To overcome this problem, emitted Sn Kalpha1 fluorescence from sample was counted using high-energy-resolution fluorescence spectrometer in the XANES measurements. Experimental energy resolution (5.0 eV) was consistent with theoretical values based on the Rowland configuration of the spectrometer. The absorption edge became steeper compared to conventional spectra. The white-line peak due to Sn(II) species became remarkably sharper and more intense in the Sn Kalpha1-detecting Sn K-edge XANES for Pt-Sn/SiO2. To support the semiclassical theory of resonant Raman scattering for the explanation of observed elimination of lifetime width, more resolved XANES data at Cu K, Pb L3, and Sn K in this work were convoluted (filtered) with a Lorentzian of each core-hole lifetime width. The processed data resembled generally well corresponding XANES spectrum measured in transmission mode. The verification based on ab initio XANES calculations was also performed.

Journal Article↗
PubMed1976

An experimental method correcting for absorption flattening and scattering in suspensions of absorbing particles: circular dichroism and absorption spectra of hemoglobin in situ in red blood cells.

An experimental approach to interpretation of the anomalous absorption and circular dichroism (CD) spectra of hemoglobin in situ in red blood cells is reported. Absorption flattening effects have been overcome by use of high cell concentratons in very short light path cuvettes. Differential scattering contributions to circular dichroism have been resolved using a CD instrument capable of variable detection geometry. Scattering effects have also been resolved using media of high refractive index to match that of the red blood cell. The results are in agreement with a parellel calculational analysis of red blood cell CD spectra, which predicted the relative magnitudes of the flattening and differential scattering CD contributions. An experimental absorption spectrum has been obtained for hemoglobin in the red blood cell with scattering and flattening eliminated. This quantitatively simulates the spectrum of a hemoglobin solution. The methods described should be widely applicable to conformational studies of macromolecules in their native environment.

Circular Dichroism↗
PubMed2005

The absorption spectrum of water near 750 nm by CW-CRDS: contribution to the search of water dimer absorption.

The absorption spectrum of natural water vapour around 750 nm has been recorded with a typical sensitivity of 3 x 10(-10) cm(-1) using a cw cavity ring down spectroscopy set up based on a Ti:sapphire laser. The 13 312.4-13 377.7 cm(-1) spectral interval was chosen as it corresponds to the region where water dimer absorption was recently measured (K. Pfeisticker et al., Science, 2003, 300, 2078-2080). The line parameters (wavenumber and intensity) of a total of 286 lines of water vapor were measured by a one by one fit of the lines to a Voigt profile. For the main water isotopologue, 276 lines were measured with line intensities as weak as 5 x 10(-29) cm molecule(-1)i.e. about 50 times smaller than the weakest H(2)16O line intensities included in the 2004 edition of the HITRAN database. On the basis of the predictions of Schwenke and Partridge, all but 16 lines could be assigned to different isotopologues of water (H(2)16O, H(2)18O, and HD16O) present in natural abundance in the sample. A total of 272 energy levels of H(2)16O were determined and rovibrationally assigned to 18 upper vibrational states. Half of them had not been reported previously. The importance of the additional absorbance resulting from the observation of many new weak lines is discussed in relation to the detection of water dimer absorption and compared to the absorbance predicted by Schwenke and Partridge. The quality of the line parameters of water monomer is shown to be of crucial importance to identify the absorbance of the water dimer in the considered region.

Journal Article↗
PubMed2001

X-ray absorption near-edge structure (XANES) spectral changes of 2-deoxy-D-ribose by irradiation within the energy region around the oxygen K-shell absorption edge.

The physicochemical characteristics of 2-deoxy-D-ribose moieties in DNA strands are important to understand biological radiation stress. So, the X-ray absorption near edge structure (XANES) of 2-deoxy-D-ribose within the energy region around the oxygen K-shell absorption edge was measured. 2-deoxy-D-ribose was exposed to 3 energies of X-rays, i.e., 526.3 eV (below O 1s-->pi*), 537.8 eV (at the absorption peak of O 1s-->sigma*) and 552.6 eV (above O 1s-->sigma*) for given periods. Slight differences in spectral changes were seen in the each irradiation energy, suggesting in fact that the chemical state and following rearranged chemical structure of 2-deoxy-D-ribose may be different between the 3 irradiation energies.

DNA↗
PubMed1987

Delta bilirubin: absorption spectra, molar absorptivity, and reactivity in the diazo reaction.

Delta bilirubin (B delta), isolated from serum, has an absorption maximum near 440 nm and a molar absorptivity of 72,000 L mol-1cm-1 in either Tris HCl (0.1 mol/L, pH 8.5) or phosphate (0.13 mol/L, pH 7.4) buffer. This absorptivity exceeds by approximately 50% and 59%, respectively, that of unconjugated bilirubin in the same buffers. This finding suggests that substantial errors can be incurred in direct spectrophotometry of bilirubins in serum. In the total diazo (TBIL) assay (Clin Chem 1985;31:1779-89), the color yield from B delta increases by 10% as the final diazo concentration is increased from 0.27 to 0.81 mmol/L. In the direct (DBIL) assay, if done in HCl (50 mmol/L), B delta yields approximately 15% more color as the diazo concentration is increased from 0.51 to 1.53 mmol/L, whereas in acetate buffer (0.4 mol/L, pH 4.7) the corresponding color yield is 25% greater. However, the absolute color yield for the reaction in HCl exceeds that in acetate buffer. In both the TBIL and the DBIL assay, B delta reacts slowly, nearly complete reaction requiring 10 min. Thus, B delta may be seriously underestimated in diazo (especially DBIL) methods in which short reaction times (20 s to 1 min) are used.

Bile↗
PubMedDate not supplied

Comparative sensitivities of flame atomic absorption spectrophotometry (AAS) and molecular absorption spectrophotometry (MAS).

A sensitivity comparison was made between conventional atomic absorption spectrophotometry (AAS) and conventional molecular absorption spectrophotometry (MAS) for the serum trace metals, copper, iron, and zinc. The sensitivity aspect considered was absorbances was obtained for concentrations in the solutions analyzed using unit lightpaths of 1 cm and 10 cm for MAS and AAS, respectively. A distinction was made between procedural sensitivity and measurement sensitivity where the latter represents molar absorptivity. Some was given to the concepts of procedural sensitization by concentration of the analyte through the use of lyophilization, extraction or ashing. The misuse of data obtained with scale expanders is described as a commonly occurring phenomenon of both AAS and MAS and a source of confusion in the understanding of measurement sensitivity.

Copper↗
PubMed1991

Evaluation of controlled release formulations: estimation of the duration of the zero-order absorption and ascertainment of absorption kinetics.

A compartmental approach for estimating the duration of the zero-order absorption was developed. For drugs obeying one-compartment model disposition, the estimation is based on an explicit relationship while an iterative process is required for drugs represented by two-compartment kinetics. A method based on a double graphical plot for ascertaining absorption kinetics for drugs exhibiting one-compartment model disposition was also developed.

Absorption↗
PubMed1994

Variable gastric emptying and discontinuities in drug absorption profiles: dependence of rates and extent of cimetidine absorption on motility phase and pH.

The influence of various fasting-state gastrointestinal parameters on variability in absorption of cimetidine was studied using simulation and cimetidine administration as a duodenal infusion and as an oral tablet in fistulated mongrel dogs. In the simulation studies, the frequency of double-peak occurrence in plasma profiles was estimated employing average gastric emptying rates as well as interdigestive-migrating-motor-complex (IMMC) phase lengths that were systematically altered. Emptying rates and phase lengths were modeled as periodic step functions. Simulations indicated that double peaks occur when gastric emptying of the drug begins in early phase I or late phase II/III, which represent the periods of very low, medium, and high gastrointestinal motility, respectively. The incidence is increased for longer phase-I duration and higher elimination rate constants. For a compound with a 2 h elimination or disposition half-life, two concentration maxima (double peaks) were found in 12% of the simulated concentration-time profiles. The double peak frequency in simulated curves was considerably higher for t1/2 < 30 min. When cimetidine was administered to dogs as a duodenal infusion in the active and quiescent motility phases, discontinuous profiles were observed, although the variability of the various parameters was reduced when compared. Pharmacokinetic models were set up that were characterized by multi-segmental input (one- to 3-lag-time models were used) for the profiles resulting from oral and duodenal administration. The lag time for the first process characterized the onset of absorption. A significant difference between phases was detected for infusions at pH 8, where the initial lag time was longer in the quiescent phase. The mean input time (MIT) was calculated as the integral input parameter. There was a tendency for the MIT to be higher for pH 6 infusions than for pH 4 and pH 8. Bioavailability analysis indicated that cimetidine was more rapidly and completely absorbed at pH 8 than at pH 6. Bioavailability was also slightly higher at pH 4 than at pH 6. We concluded that gastric emptying increased the variability of the cimetidine concentration-against-time profiles and that it plays a role with respect to double-peak occurrence, although it is only one of several causative factors.

Administration, Oral↗
PubMed2004

Assessment system for dioxin absorption in the small intestine and prevention of its absorption by food factors.

It has been reported that 90% of the amount of dioxin in the whole body is absorbed orally with food. However, a concise and simple system to assess dioxin absorption in the small intestine has not yet been established. The present study reports a new in vitro assessment system for this purpose. A stable dioxin-responsive cell line was established by introducing a plasmid that incorporates a xenobiotic-responsive element upstream of the luciferase gene into human hepatic HepG2 genomic DNA. Dioxin was added to the apical side of differentiated human intestinal epithelial Caco-2 cell monolayers that had been cultured on a semipermeable membrane, and the basal medium was recovered after an appropriate incubation time. To the recovered medium was added dioxin-responsive HepG2, and a luciferase assay was performed. The established stable cell line clearly showed dose-and time-dependent response to dioxin. When a food factor such as chlorophyll, which has been reported to increase dioxin excretion in in vivo studies, was added with dioxin, a significant decrease in dioxin permeability to the Caco-2 monolayer was observed. This assessment system would be useful to search for those food factors that could prevent dioxin absorption in the small intestine.

Carcinoma, Hepatocellular↗
PubMed1977

Effect of surfactants on absorption through membranes V: Concentration-dependent effect of a bile salt (sodium deoxycholate) on absorption of a poorly absorbable drug, phenolsulfonphthalein, in humans.

The effect of administration of 600-and 300-mg doses of sodium deoxycholate 1 hr before phenolsulfonphthalein solution is reported. The 600-mg dose caused a decrease in drug bioavailability as measured by the total amount excreted in 24 hr. The 300-mg dose cause and increase in the initial phenolsulfonphthalein absorption rate, suggesting a direct action of the bile salt on membrane permeability. The decrease in absorption upon administration of 600 mg was attributed to micellar entrapment of the drug molecule.

Adult↗
PubMed1981

Intestinal absorption mechanism of amphoteric beta-lactam antibiotics I: Comparative absorption and evidence for saturable transport of amino-beta-lactam antibiotics by in situ rat small intestine.

The disappearance of various beta-lactam antibiotics from in situ rat small intestinal loops was studied at pH 7.4. For monobasic penicillins, despite the wide variety of apparent partition coefficients in isobutyl alcohol-water, the disappearance from the jejunal loops was almost 30% (+/- 5% SD). On the other hand, the disappearance of amphoteric derivatives of penicillins and cephalosporins having very low lipid solubility varied widely between 12 and 80%. The peak blood levels after intraduodenal administration to the rats correlated well with the extent of disappearance of amphoteric penicillins from the intestinal loops. Absorption studies utilizing in situ intestinal loops were performed at variable dose ranges to yield a clear dose-dependent disappearance. It is suggested that certain carrier-mediated transport systems underlie the absorption mechanism of amphoteric beta-lactam antibiotics.

Animals↗
PubMed1981

Intestinal absorption mechanism of amphoteric beta-lactam antibiotics II: Michaelis-Menten kinetics of cyclacillin absorption and its pharmacokinetic analysis in rats.

The absorption of cyclacillin at pH 7.0 by the rat small intestine was investigated using in situ perfusion. At the lowest dose of 95 microgram/ml, the antibiotic disappearance was rapid and followed first-order kinetics, with the disappearance being 85% at 100 min. At the intermediate concentrations of 770 and 1200 microgram/ml, the disappearance after 100 min was 69 and 54%, respectively, and semilogarithmic plots clearly showed convex curvatures. At the highest concentration of 30 mg/ml, cyclacillin disappeared slowly from the perfusate, in an apparent first-order fashion. The disappearance was 26% after 100 min of perfusion and was similar in extent at 5.2 mg/ml. This concentration-time profile was satisfactorily fitted to the simultaneous Michaelis-Menten and first-order kinetic equations. The area under the blood concentration versus time curve (AUC) after a single intraduodenal dose of cyclacillin was almost consistent with the AUC after the equivalent intravenous dose (10 mg/kg). Additional evidence from a pharmacokinetic analysis of steady-state blood concentrations after constant infusion of cyclacillin through the portal vein and the small intestinal lumen indicated that cyclacillin absorption by the rat intestinal tissue at relatively low concentrations (less than 1 mg/ml) followed solely Michaelis-Menten kinetics. Cyclacillin may be transported by certain types of carrier-mediated mechanisms.

Animals↗