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Molecularly imprinted polymers (MIPs) using p-hydroxybenzoic acid (p-HB), p-hydroxyphenylacetic acid (p-HPA) and p-hydroxyphenylpropionic acid (p-HPPA) as templates were synthesized. The performance of the templates and their analogues on polymer-based high performance liquid chromatography (HPLC) columns was studied. The imprinting effect of the MIP using p-HB as template is more obvious than that of MIP using either p-HPA or p-HPPA as template, and the mixture of p-HB and p-HPA can be well separated on the MIP using p-HB as template, but not on the blank. Interestingly, the recognition of MIP (p-HB as the template) to p-HB showed a synergistic effect. The retention factor of p-HB is not the sum of those of phenol and benzoic acid. We also found that the imprinting effect decreased when increasing the concentration of acetic acid in mobile phase. The possible reason is that acetic acid molecules occupied the binding sites of the polymer, thereby decreasing the concentration of binding sites. Furthermore, polymers, which showed specificity to 3,4-dihydroxybenzoic acid, can be prepared with p-HB as template. It is thus possible to synthesize a specific polymer for a compound that is either expensive or unstable by using a structurally similar compound as template.
Fish and shellfish supply the human diet with not only complex nutrients including the omega-3 fatty acids, but also highly toxic chemicals including methylmercury. The dietary essential fatty acids are linoleic and alpha-linolenic acid. Two omega-3 fatty acids with longer carbon chains, eicosahexaenoic acid (EPA) and docosahexaenoic acid (DHA), can be synthesized in humans from alpha-linolenic precursors. Though not required in the diet per se, EPA and DHA have important roles in metabolism. The almost exclusive source of preformed dietary DHA is fish and shellfish. These foods are also an important source of EPA. In marked contrast to the benefits of fish and shellfish as sources of preformed omega-3 fatty acids, fish and shellfish are almost exclusively the dietary source of methylmercury. Fortunately, these chemicals are not uniformly distributed across many species of fish and shellfish. The purpose of this article is to provide information on the comparative distribution of these chemicals and nutrients to help groups formulating dietary recommendations.
A high-performance liquid chromatographic method was applied to the determination of gallic acid, albiflorin, paeoniflorin, ferulic acid and benzoic acid in Si-Wu decoction and other 13 combinations of the formula. These five compounds were analyzed simultaneously with a Zorbox SB C-18 column by gradient elution using 0.01% (v/v) phosphoric acid-acetonitrile as the mobile phase. The flow rate was 1 ml min(-1), and detection was set at 230 nm. The recovery of the method was in the range of 94.8-103.1%, and all the compounds showed good linearity (r>0.9995) in a relatively wide concentration range. The result indicated that the content of these five compounds changed after decocting process. The contents of paeoniflorin, albiflorin, ferulic acid and gallic acid increased and that of benzoic acid decreased significantly.
A study of the conjugal transfer of ColV,I-K94 tn 10 from acid-treated donors suggested that acid-habituated recipients repair acid-damaged plasmid DNA better than those that are not habituated. The presence of an increased repair activity for acid-damaged DNA in habituated cells was confirmed by isolating pBR322 from acid-treated organisms; habituated cells produced more transformants when transformed by it than did non-habituated ones. Additionally, agarose gel electrophoretic studies of pBR322 DNA isolated from acid-damaged cells and tests of its transforming activity both indicated that plasmid DNA in habituated cells is less damaged by extreme acidity than is that in non-habituated organisms.
Holloman ((1975) J. Biol. Chem. 250, 2993-3000) reported the isolation from Ustilago maydis of a glycoprotein which prevented the precipitation of nucleic acids in cold 5% trichloroacetic acid. Two glycoprotein fractions from U. maydis with this nucleic acid-solubilizing activity were isolated in our laboratory using improved purification procedures. The activity was not due to nuclease contamination. The glycoproteins are distinguished by: their ability to bind to concanavalin A-Sepharose; their differential binding to double- and single-stranded deoxyribonucleic acid, and to ribonucleic acid; their molecular weights (46,000 and 69,000); and the relative amounts present in growing versus nongrowing cells. Both fractions required sulfhydryl-reducing conditions for optimal yields, specific activity, and stability. Nucleic acid binding was cooperative, the minimum number of glycoproteins required to make a native T7 DNA molecule soluble in dilute acid being estimated at 2 and 15, respectively.
In livers of rats fed a single morning dose of 100 mg tetradecylthioacetic acid (TTA) total long-chain acyl-CoA increased significantly to 3 times control levels within 6 h, then the level declined almost to control value within the next morning. Hepatic malonyl-CoA was reduced 75% 6 h after TTA treatment. From 6 to 24 h malonyl-CoA increased about 10-fold to about 3 times that of controls. Paradoxically there was nearly a 2-fold higher oxidation of both [1-14C]palmitic acid (0.5 mM) and [1-14C]oleic acid (0.5 mM) in hepatocytes isolated from rats 24 h after TTA treatment compared to controls. After 6 h, when malonyl-CoA was at a minimum in vivo, fatty acid oxidation in cells was not increased. Acylcarnitine formation in digitonin permeabilized hepatocytes isolated 24 h after administration of TTA was increased both in the absence and in the presence of malonyl-CoA. At 24 h peroxisomal palmitoyl-CoA oxidase activity was not increased. The results suggest that an increased CPT activity and increased acylcarnitine formation in the presence of malonyl-CoA is a delayed response to increased acyl-CoA levels. Furthermore, in hepatocytes isolated after 24 h incorporation of [1-14C]oleic acid into triacylglycerols was significantly reduced. The data show that in hepatocytes isolated from rats 24 h after administration of a single dose of TTA, there is a diversion of hepatic acyl-CoA from synthesis of triacylglycerols into beta-oxidation in the mitochondria.
Administration of doses of linoleic acid (LA) up to 36 g/d in humans raised blood levels of linoleic acid but not of its metabolites. This is probably because the conversion of LA to gamma-linolenic acid (GLA) is slow and rate-limiting. We have found that administration of relatively small amounts of GLA, up to 360 mg/d, raises human blood levels of dihomogammalinolenic acid (DGLA) and arachidonic acid (AA).
The pharmacokinetics of valproic acid (VPA) and three structural analogs, octanoic acid (OA), cyclohexanecarboxylic acid (CCA), and 1-methyl-1-cyclohexanecarboxylic acid (MCCA), were examined in female Sprague-Dawley rats. All four carboxylic acids evidenced dose-dependent disposition. A dose-related decrease in total body clearance was observed for each test compound, suggesting the presence of saturable elimination processes. Furthermore, the apparent volume of distribution for these compounds was, with the exception of CCA, dose-dependent, indicating that binding to proteins in serum and/or tissues may be saturable. Both VPA and MCCA exhibited enterohepatic recirculation, although the degree of recirculation appeared to be dose- and compound-dependent. Significant quantities of both VPA and MCCA were excreted in the urine as base-labile conjugates, presumably representing glucuronides. In contrast, OA and CCA were not excreted in the urine as base-labile conjugates and did not evidence enterohepatic recirculation. CCA displayed apparent Michaelis-Menten kinetics, although the calculated Km was dose-dependent. The results suggest that relatively minor changes in chemical structure have a marked influence on the metabolism and disposition of low molecular weight carboxylic acids.
Patients undergoing elective cholecystectomy provide a highly reproducible model of the effects of trauma on intermediary metabolism. Three parenteral nutrition regimens were given to groups of eight such patients. An isonitrogenous total parenteral nutrition, including a commercially available amino acid solution, an amino acid solution enriched with branched chain amino acids or one supplemented with ornithine-alpha-ketoglutarate, was given after operation. The intra cellular free amino acid concentrations of skeletal muscle were determined in tissue specimens obtained before operation and on the third postoperative day using a percutaneous needle biopsy technique. The mean (s.e.m.) decrease in the concentrations of free intracellular glutamine on the third postoperative day was less pronounced (P less than 0.05) in the ornithine-alpha-ketoglutarate group (18.8(7.5)per cent) than in the control group (39.4(5.1)per cent) or the branched chain amino acid group (45.3(6.1)per cent). In conclusion, in the immediate postoperative period total parenteral nutrition supplemented with ornithine-alpha-ketoglutarate countered the decline in the muscle free glutamine. No difference in this parameter was seen between the control group and the branched chain amino acid group.
Bidirectional transport studies were conducted to determine whether substrates of five intestinal transporters showed carrier-mediated asymmetric transport across MDCK (Madin-Darby canine kidney) cell monolayers grown under standard conditions. Drug concentrations were quantitated using liquid scintillation counting, liquid chromatography/mass spectrometry/mass spectrometry, or liquid chromatography/mass spectrometry. In the presence of a pH gradient, benzoic acid exhibited net apical-to-basolateral transport, with apparent permeability ratios (apical-to-basolateral permeability/basolateral-to-apical permeability) ranging from 14 to 25. The addition of valproic acid reduced the permeability ratio by 70-90%. Cephalexin transport also exhibited net absorption in the presence of a pH gradient, with apparent permeability ratios ranging from 14 to 71, depending on growth conditions. Radiolabeled phenylalanine exhibited a low level of carrier-mediated absorption with an apparent permeability ratio of 1.8 that was reduced to 1.0 in the presence of unlabeled L-phenylalanine. Taurocholic acid did not exhibit carrier-mediated absorption. Cyclosporine and fexofenadine exhibited P-glycoprotein-mediated efflux from both MDCK and Caco-2 cells, which was more sensitive to inhibition in MDCK cells. These results suggest that although MDCK cell monolayers may be a useful model for evaluating transport by the absorptive monocarboxylic acid and peptide transporters and the efflux transporter, P-glycoprotein, they are not useful for predicting large neutral amino acid or bile acid transport in the intestine.
Stable-isotope-labelled (2H6, 18O) 3-hydroxy-3-phenylpropanoic acid, a putative intermediate in the biosynthesis of benzoic acid (BA) and salicylic acid (SA) from cinnamic acid, has been synthesized and administered to cucumber (Cucumis sativus L.) and Nicotiana attenuata (Torrey). Analysis of the products by gas chromatography-mass spectrometry revealed incorporation of labelling into BA and SA, but not into benzaldehyde. In a separate experiment, 3-hydroxy-3-phenylpropanoic acid was found to be a metabolite of phenylalanine, itself the primary metabolic precursor of BA and SA. These data suggest that cinnamic acid chain shortening is probably achieved by beta-oxidation, and that the proposed "non-oxidative" pathway of side-chain degradation does not function in the biosynthesis of BA and SA, in cucumber and N. attenuata.