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Query: UMLS:C0220723 (PCA)
 4,687 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The structural changes in the lipid of the excised skin of nude mice and the porcine stratum corneum was investigated by in vitro treatment with vitamin C, oleic acid, or DMSO. The CH2 stretching vibrational peaks of lipid near 2920 cm-1 (asymmetric) and 2850 cm-1 (symmetric) shifted to higher wavenumber due to the lipid-disorder after in vitro treatment with above enhancers. The spectral shift of the asymmetric CH2 band was more sensitive than that of the symmetric CH2 band. The higher wavenumber of CH2 stretching bands decreased gradually to the lower region after co-treatment or posttreatment with pyrrolidone carboxylate sodium (PCA Na). Such a decrease was dependent on the PCA Na concentration and the time of treatment. The higher the concentration of PCA Na used, the lower value of the permeability coefficient of vitamin C through the excised skin and the downward spectral shift of asymmetric CH2 band were obtained. When PCA Na coexisted with vitamin C in the cell donor compartment, a competitive effect between PCA Na and vitamin C was found. The oleic acid was supposed to directly insert it into the lipid structure to form a rigid structure, leading to larger spectral shift of both stretching bands but lesser restoring ability after PCA Na treatment. However, DMSO only displaces water from the lipid head groups and protein domain of skin to indirectly loosen the lipid structure, resulting in lesser spectral shift of the CH2 stretching bands to higher region, which was easier and better restoration after PCA Na application. The PCA Na enabled to restore the disordered lipid structure to order state might be attributed to PCA Na previously penetrated into skin and then absorbed water to directly or indirectly rearrange the disordered lipid bilayer structure.
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PMID:Direct or indirect skin lipid-ordering effect of pyrrolidone carboxylate sodium after topical treatment with penetration enhancers. 777 46

The amount of endotoxin in the serum was measured by the new assay method of endotoxin using a filtercup, Limulus amebocyte lysate, and immobilized histidine which is a specific adsorbent for endotoxin. The maximum recovery of endotoxin in the rabbit serum was obtained using acetate buffer (pH 5.5, mu = 0.1) for the adsorption. Using this buffer, various kinds of endotoxin in water were adsorbed quantitatively on immobilized histidine, and the activity of the adsorbed endotoxin was well recovered. The value of the amount of endotoxin in the bovine serum measured by the new assay method, which includes heat treatment (70 degrees C, 10 min) after separation followed by washing, was closer to that calculated from pyrogenic activities in rabbits than that measured by the PCA-Toxicolor method.
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PMID:[Specific assay for endotoxin using immobilized histidine. Application to serum sample]. 780 81

As the cell membranes are one of the targets of drug treatment in cancer cells, their membrane composition and variations in this composition need to be analyzed. Gradient selected 2D-NMR inverse heteronuclear chemical shift correlations are have described, which offer optimum sensitivity combined with a high reliability for unequivocal signal assignment in proton, carbon and phosphorous spectra, concerning neutral lipids and in particular phospholipids. Additionally, an extraction procedure is presented to extract subsequently the water soluble (PCA extract) and lipophilic metabolites (chloroform/methanol extract) from the same cell batch.
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PMID:Combined extraction techniques of tumour cells and lipid/phospholipid assignment by two dimensional NMR spectroscopy. 869 10

Experimental methods for octanol/water partition coefficient (logP) determination are surveyed. The terminology used in the literature, the lipophilicity/pH profile and the most important factors influencing the logP values have been discussed. Several new, recently developed direct logP determination methods are introduced including their advantages and limits of application. Some aspects of good laboratory practice of the shake-flask method are described and results of a validation study of pH-metric logP determination technique used PCA 101 pKa and logP analyser (Sirius, UK) are also shown. Questions have to be answered in method selection for logP measurement are summarized in flow chart (Fig. 8). The author based on her own experiences in lipophilicity measurements over decades, suggests the shake-flask method and the automated dual-phase potentiometric technique, as approaches fulfilling the GLP rules.
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PMID:[Practical aspects of partition measurements according to GLP rules]. 943 65

Prediction of outcome after shunt-therapy in chronic hydrocephalus syndrome is uncertain. Pathology reveals an impairment of cerebral blood flow (CBF). Based on this, we evaluated CBF and its significance for the assessment of prognosis. In 21 patients (mean age 69 years) selected for surgery, CBF was measured by PET (15O-H2O) before, about one week and 7 months (n = 14) after shunting. CBF was computed by a 1-compartmental model in the territories of the ACA, MCA and PCA. One PET slice in the height of the maximum projection of both cellae mediae was chosen. CBF data were standardized by cluster analysis. Three CBFClusters with significantly different CBF levels prior to shunting in the ACA, MCA and PCA territory, respectively, referred to the sample average (38.2 ml/100 ml/min) were found. These CBFClusters differed in clinical outcome: almost 50% and 90% of patients improved clinically in CBFCluster I, with a perfusion level lower than average, after one week and 7 months, respectively. In contrast, patients of CBFCluster II with an average perfusion did not improve. CBF changes 7 months after shunting related to global CBF before surgery showed a relationship with the clinical course. Clinical outcome corresponded with preoperative global CBF values. Cerebral blood flow lower than average forecasts clinical improvement. Our results suggest that measurement of CBF adds to the indication for surgery.
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PMID:Cerebral blood flow in chronic hydrocephalus--a parameter indicating shunt failure--new aspects. 977 26

/ Recent focus has been placed on ecoregion delineations for providing an appropriate framework for monitoring and assessment of region-specific attainable water/habitat quality. Using an ecoregion approach to stratify variance, this study was conducted to determine whether earlier (subjectively) selected Swedish reference lakes may be considered as regionally representative reference sites when compared with a randomly selected lake population. Predictive modeling by discriminant function analysis with lakes classified by ecoregion and lake surface area and six physicochemical variables showed that the greater majority of reference lakes may be considered as regionally representative. The highest proportion of lake "misclassifications" occurred in the boreonemoral ecoregion, a relatively diverse ecoregion of southern Sweden. This apparent bias may be in part be due to the criteria used in selecting regional reference lakes. In the earlier selection of reference lakes emphasis was placed on lakes not being adversely affected by land usage or pollutant discharges, consequently forest lakes were often overrepresented and sites in agricultural areas underrepresented in the selected reference sites. As a complement to predictive modeling, PCA ordination showed the placement of reference lakes within the random lake population and indicated where reference sites might be missing along potentially important ecological gradients. KEY WORDS: Regionalization; Ecoregion; Representativeness; Reference; Ordination; Modeling; Temperate lakes
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PMID:Regional Representativeness of Swedish Reference Lakes. 981 76

The anti-allergic actions of the leaves of Castanea crenata (Fagaceae) were studied. The water extract demonstrated potent anti-allergic actions in in vivo and in vitro experiments. The oral or intraperitoneal administration of the extract (100 or 200 mg/kg) caused a significant inhibition of the 48 hr-PCA (up to 90%) and the vascular permeability induced by histamine or serotonin in rats (about 80%). The anaphylactic release of beta-hexosaminidase from RBL-2H3 cells was also significantly inhibited by the extract in a dose-dependent manner with an IC50 value of 230 microg/ml. The activity-guided fractionation of the extract, based on the determination of inhibitory effect upon the release of beta-hexosaminidase, led to the isolation of quercetin as an active principle responsible for the inhibition of degranulation.
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PMID:Anti-allergic actions of the leaves of Castanea crenata and isolation of an active component responsible for the inhibition of mast cell degranulation. 1040 40

The retention properties of eight alkyl, aromatic, and fluorinated reversed-phase high-performance liquid chromatography bonded phases were characterized through the use of linear solvation energy relationships (LSERs). The stationary phases were investigated in a series of methanol/water mobile phases. LSER results show that solute molecular size and hydrogen bond acceptor basicity under all conditions are the two dominant retention controlling factors and that these two factors are linearly correlated when either different stationary phases at a fixed mobile-phase composition or different mobile-phase compositions at a fixed stationary phase are considered. The large variation in the dependence of retention on solute molecular volume as only the stationary phase is changed indicates that the dispersive interactions between nonpolar solutes and the stationary phase are quite significant relative to the energy of the mobile-phase cavity formation process. PCA results indicate that one PCA factor is required to explain the data when stationary phases of the same chemical nature (alkyl, aromatic, and fluoroalkyl phases) are individually considered. However, three PCA factors are not quite sufficient to explain the whole data set for the three classes of stationary phases. Despite this, the average standard deviation obtained by the use of these principal component factors are significantly smaller than the average standard deviation obtained by the LSER approach. In addition, selectivities predicted through the LSER equation are not in complete agreement with experimental results. These results show that the LSER model does not properly account for all molecular interactions involved in RP-HPLC. The failure could reside in the V2 solute parameter used to account for both dispersive and cohesive interactions since "shape selectivity" predictions for a pair of structural isomers are very bad.
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PMID:Comparative study of hydrocarbon, fluorocarbon, and aromatic bonded RP-HPLC stationary phases by linear solvation energy relationships. 1046 78

Five brands of French bottled mineral water were analyzed by heterotrophic plate counts (HPC) and for the presence of multiple antibiotic resistant bacteria. HPC at 22 degrees C were around 10(4) colony forming units ml(-1) on R2A medium. Enumeration on PCA/10, MH, and especially PCA and King B media was less efficient. At 37 degrees C, HPC were two to three orders of magnitude less than at 22 degrees C. Moreover, phenotypic diversity (7 to 15 phenotypes) was optimal on R2A incubated at 22 degrees C. All isolates were identified as non-fermentative Gram-negative rods and 75% were non-identifiable with the API 20NE system. Stenotrophomonas maltophilia and fluorescent Pseudomonas were isolated on VIA and CFC selective agar media, respectively. Burkholderia cepacia strains were not isolated on BCSA medium. The species S. maltophilia was found in 33%, 28%, and 11% of sample from springs A, D, and E, respectively. Independent of brand, isolates from HPC media were less efficient to achieve confluent growth in 18 h on MH at 30 or 37 degrees C (0 to 40%) than isolates from selective media (28 to 63%). Seventy percent of the total isolates from dominant microflora (1-5 x 10(3) CFU ml(-1) on HPC media) were resistant against two or four antibiotics. The antibiotics concerned were principally aztreonam, ampicillin, and nalidixic acid. The remaining dominant bacteria showed a 6-9 multiple antibiotic resistant (MAR) pattern. All isolates were susceptible to newer antimicrobial agents. Owing to their low nutrient and temperature requirements, these isolates are unlikely to cause concern to public heath. Fifty percent of strains isolated from selective media (non-dominant microflora, 4-40 CFU l(-1)) showed a 10-18 MAR pattern and 33%, identified as S. maltophilia, a 20-27 MAR pattern. However, minocycline was effective against all isolates. Owing to its low concentration, colonization of human intestine by MAR S. maltophilia is unlikely.
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PMID:Occurrence and Multiple Antibiotic Resistance Profiles of Non-fermentative Gram-Negative Microflora in Five Brands of Non-carbonated French Bottled Spring Water. 1088 37

NH(4)Cl (10 mM) caused a sustained increase in the cell volume in immobilized, perfused F98 glioma cells to approx. 125% of control after 3 h, as measured by diffusion-weighted (1)H NMR spectroscopy. Concomitantly, the glutamine (Gln) concentration increased by 130%, accompanied by a marked decrease in cytosolic osmolytes, i.e. myo-inositol and taurine, determined from (1)H NMR spectra of PCA extracts. Inhibition of Gln synthetase partially prevented the increase in water content. While losses of organic osmolytes are also observed under hypotonic conditions, the rapid cell swelling is followed by the regulatory cell volume decrease (RVD), and is accompanied by decreased cytosolic Gln. We suggest that the rise in intracellular osmolarity, which is attributed to NH(4)Cl metabolism to Gln, but also to alanine (Ala), is not compensated by the release of other osmolytes, and causes cell swelling without RVD.
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PMID:Effects of ammonia exposition on glioma cells: changes in cell volume and organic osmolytes studied by diffusion-weighted and high-resolution NMR spectroscopy. 1111 Nov 63


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