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At least 1,153 records · Page 64Linked to original sources
PubMed1999

Separation and simultaneous determination of nalidixic acid, hydroxynalidixic acid and carboxynalidixic acid in serum and urine by micellar electrokinetic capillary chromatography.

Separation in capillary electrophoresis is governed by various factors, including buffer type, buffer concentration, pH, temperature, voltage and micelles. Through proper adjustment of these parameters, nalidixic acid and its two major metabolites, 7-hydroxynalidixic and 7-carboxynalidixic, could be separated by micellar electrokinetic capillary chromatography using an electrophoretic electrolyte consisting of 50 mM borate buffer (pH 9) containing 25 mM sodium dodecyl sulphate and 10% acetonitrile. A linear relationship between concentration and peak area for each compound was obtained in the concentration range 0.15-100 micrograms ml-1, with a correlation coefficient greater than 0.999 and detection limits in the 0.2-0.7 ng ml-1 range. Intra- and inter-day precision values of about 0.8-1.2% RSD (n = 11) and 1.3-2.0% RSD (n = 30), respectively, were obtained. The method has been applied to the analysis of nalidixic acid and its two major metabolites in serum and urine with limits of sensitivity lower than 0.8 ng ml-1.

Chromatography, Micellar Electrokinetic Capillary↗
PubMed1966

Ribonucleic acid synthesis by Escherichia coli C 3000/L after infection by the ribonucleic acid coliphage ZIK/1, and properties of the coliphage-induced double-stranged ribonucleic acid.

1. The efficiency of extracting nucleic acids from Escherichia coli after five methods of obtaining cell lysis was determined. 2. The recovery of various nucleic acid species isolated after chromatography on methylated albumin-coated kieselguhr was also examined. 3. Double-stranded coliphage-induced RNA was isolated from infected bacteria and its resistance to ribonuclease digestion under various conditions determined. 4. The involvement of double-stranded RNA during the infection process was demonstrated. 5. The time-course of the syntheses in infected cells of double-stranded RNA, DNA, single-stranded coliphage and 16s ribosomal RNA, transfer RNA and ribosomal 23s RNA was examined. 6. It was demonstrated that the syntheses of DNA, transfer RNA and ribosomal RNA decreased 10-15min. after infection. 7. Synthesis of coliphage RNA commenced 10-15min. after infection and double-stranded RNA was also synthesized from about 10min. after coliphage adsorption.

Bacteriolysis↗
PubMed2003

The epimeric 9-oxobicyclo[3.3.1]nonane-3-carboxylic acids: hydrogen-bonding patterns of the endo acid and the lactol of the exo acid.

The two delta-keto carboxylic acids of the title, both C(10)H(14)O(3), are epimeric at the site of carboxyl attachment. The endo (3alpha) epimer, (I), has its keto-acid ring in a boat conformation, with the tilt of the carboxyl group creating conformational chirality. The molecules form hydrogen bonds by centrosymmetric pairing of carboxyl groups across the corners of the chosen cell [O...O = 2.671 (2) A and O-H...O = 179 (2) degrees ]. Two close intermolecular C-H...O contacts exist for the ketone. The exo (3beta) epimer exists in the closed ring-chain tautomeric form as the lactol, 8-hydroxy-9-oxatricyclo[5.3.1.0(3,8)]undecan-10-one, (II). The molecules have conformational chirality, and the hydrogen-bonding scheme involves intermolecular hydroxyl-to-carbonyl chains of molecules screw-related in b [O...O = 2.741 (2) A and O-H...O = 177 (2) degrees ].

Bridged Bicyclo Compounds↗
PubMed1971

Oxidation of nicotinic acid by a Bacillus species: source of oxygen atoms for the hydroxylation of nicotinic acid and 6-hydroxynicotinic acid.

Three types of evidence are presented to show that the enzymes that hydroxylate nicotinic acid to 2,6-dihydroxynicotinic acid use water as a source of oxygen atoms. (18)O is incorporated into the products from H(2) (18)O. Molecular oxygen acts as a terminal electron acceptor, one-half molecule being consumed per molecule of hydroxyl groups incorporated. An external electron acceptor is required for activity in purified preparations.

Bacillus↗
PubMed1974

Attempts to detect deoxyribonucleic acid from Agrobacterium tumefaciens and bacteriophage PS8 in crown gall tumors by complementary ribonucleic acid-deoxyribonucleic acid-filter hybridization.

Labeled ribonucleic acid (RNA) complementary to Agrobacterium tumefaciens DNA and PS8 bacteriophage DNA (cRNA) were used in a systematic study of the sensitivity of cRNA/deoxyribonucleic acid (DNA)-filter hybridization for detection of small amounts of phage or bacterial DNA immobilized on filters. A. tumefaciens cRNA of specific activity 10(6) to 2 x 10(6) counts per min per mug reacted to a significant extent when the DNA-filter contained 1% A. tumefaciens DNA in a salmon DNA background, but 0.1% A. tumefaciens DNA was not detectable. PS8 phage cRNA of the same specific activity reacted to a significant extent when the DNA-filter contained as little as 0.01% PS8 DNA in a salmon DNA background. Both kinds of cRNA were found to bind to tobacco crown gall tumor DNA-filters. Similar reaction was found with control normal callus DNA-filters but not with tobacco seedling DNA-filters. The "hybrids" formed by cRNA with normal callus and tumor DNA-filters had low thermal stability. Attempts to purify the tumor and normal callus DNA prior to immobilization on the filter resulted in elimination of this spurious binding. No evidence was found for bacterial or phage DNA in crown gall tumor DNA.

Bacteriophages↗
PubMed1969

Characterization of excess deoxyribonucleic acid synthesized by pneumococci in the presence of polyadenylic acid and deoxyribonucleic acid precursors.

Excess deoxyribonucleic acid (DNA) synthesized by cell suspensions of encapsulated pneumococci in the presence of polyadenylic acid plus all eight of the naturally occurring deoxyribonucleosides and deoxyribonucleotides has been characterized in several ways. The DNA represents complete molecules, is synthesized by a relatively large population at a steady rate, and is replicated in a semiconservative manner.

Adenine Nucleotides↗
PubMed1989

Potential bile acid metabolites. XV. Synthesis of 4 beta-hydroxylated bile acids; unique bile acids in human fetal bile.

The 4 beta-hydroxylated derivatives of lithocholic, deoxycholic, chenodeoxycholic, and cholic acids were synthesized from their respective parent compounds. The principal reactions employed were 1) beta-face cis-dihydroxylation of delta 3 intermediates with osmium tetroxide-N-methylmorpholine N-oxide, 2) selective cathylation of vicinal 3 beta,4 beta-diols followed by oxidation of the resulting 4 beta-monocathylates, or direct selective oxidation at C-3 of 3 beta,4 beta-diols with pyridinium chlorochromate, and 3) stereoselective reduction of the 3-oxo compounds with tert-butylamine-borane complex. The results of analysis of the prepared 4 beta-hydroxylated bile acids with a diequatorial trans-glycol structure and their 3 beta-epimers by proton and carbon-13 nuclear magnetic resonance spectroscopies are briefly discussed along with the mass spectrometric properties.

Bile↗
PubMed1976

Bile acid glucuronides, III[1, 2]. Chemical synthesis and characterization of glucuronic acid coupled mono-, di- and trihydroxy bile acids.

The synthesis of bile acid-3-beta-D-monoglucuronides has been accomplished via the Koenigs-Knorr condensation reaction using methyl 2, 3, 4-tri-O-acetyl-1-deoxy-alpha-bromo-D-glucopyranuronate as coupling reagent. Chemical characteristics as melting points, elemental analyses, IR-spectra, isobutane-chemical ionization mass spectra and, in case of the derivative of 3alpha-hydroxy=5beta-cholanoate, NMR-spectra were recorded and can serve as a means of identification of these recently detected naturally occurring derivatives of bile acids in isolation procedures from biological sources.

Bile Acids and Salts↗
PubMed1994

Disposition of 5-aminosalicylic acid and N-acetyl-5-aminosalicylic acid in fetal and maternal body fluids during treatment with different 5-aminosalicylic acid preparations.

STUDY OBJECTIVE: To determine the concentration of 5-aminosalicylic acid (5-ASA) and the metabolite N-acetyl-5-aminosalicylic acid (Ac-5-ASA) in the maternal and fetal plasma at delivery and in the maternal milk post partum. DESIGN AND STUDY SUBJECTS: Pregnant and lactating women with chronic inflammatory bowel disease, treated with different pure 5-ASA preparations participated in the study. At delivery, samples of fetal and maternal plasma were obtained from nine women. The excretion in milk was measured and the time of medicine intake was registered during a 24 h period 2-4 weeks after delivery in 13 women. RESULTS: Concentrations of 5-ASA in the fetal plasma were lower than in maternal plasma. Plasma concentrations of Ac-5-ASA were detectable in all the nine samples and similar levels in the mother and the fetus were found at the time of delivery. In three women 5-ASA was detected in the milk in low concentrations. The concentration of Ac-5-ASA in the milk varied considerably during the 24 h collection period, and also between individuals; its concentration tended to be higher than in the plasma. No time relation between medicine intake and maximal concentration in the milk was found. Based on the maximal Ac-5-ASA concentration and a milk intake of one liter/daily, the newborn receives less than 15 mg Ac-5-ASA daily. CONCLUSION: The study indicates that treatment with pure 5-ASA preparations in conventional doses is without risk to the fetus and the newborn.

Aminosalicylic Acids↗
PubMed1976

Effect of tryptophan on polyriboadenylic acid and polyadenylic acid-messenger ribonucleic acid in rat liver.

The administration of tryptophan to fasted rats 1 hour before killing resulted in marked increases in the amounts of hepatic polyriboadenylic acid (poly(A)) and poly(a)-containing-mRNA in the cytoplasm and a shift in hepatic polyribosomes toward heavier aggregates. When animals were treated with cordycepin, or actinomycin D, to both, there was disaggregation of hepatic polyribosomes and inhibition of poly(A) synthesis. Administration of tryptophan to fasted animals pretreated with cordycepin, or actinomycin D, or both induced a shift in hepatic polyribosomes toward heavier aggregates and an increase in in vitro protein synthesis. Fasted rats that received [U-14C] adenosine to prelabel hepatic poly (A) and then were treated with cordycepin, or actinomycin D, or both before tubefeeding tryptophan revealed increased hepatic levels of labeled polyribosomal poly (A) in comparison with controls. Fasted rats that received 14C-orotic acid to prelabel poly (A)-mRNA and then were treated with actinomycin D after 1 hour and with tryptophan along with cycloheximide after 1 1/2 hours revealed marked increases in labeling of hepatic poly (A)-mRNA associated with polyribosomes in comparison with controls. These findings suggest that tryptophan may act to stimulate the transport of poly (A)-containing-mRNA into the cytoplasm of the liver.

Adenosine↗
PubMed1990

Watersoluble synthetic nucleic acid analogs--polyethyleneimine derivatives containing nucleic acid bases--conformation and interactionwith nucleic acids.

Water soluble polyethyleneimine derivatives containing nucleic acid bases were found to interact with polynucleotides, DNA, RNA. The conformational change by formation of complex was observed by CD spectra and was discussed with the hypochromicity in UV spectra. The rates of interactions between nucleic acid bases in polymers were slow as shown by UV spectra, but the conformational changes of the polynucleotides were fast as shown by CD spectra. In the case of the uracil derivative (PEI-Hse-Ura), high value of CD spectra [theta] 2.80 = -8.0 x 10(-4) for the complex with DNA might be caused by psi type conformation of DNA.

Circular Dichroism↗
PubMed1984

Excitatory amino acid receptor interactions of a novel alpha-phosphinic acid analogue of alpha-methylaspartic acid.

An alpha-phosphino analogue of alpha-methylaspartate has been synthesized. The compound may not interact with excitatory amino acid receptors directly, as assessed by direct in vitro radioreceptor binding methods; however, it possesses weak anticonvulsant activity and exhibits an excitant action in vitro that is apparently not mediated by a N-methyl-D-aspartate receptor.

Acetylcholine↗
PubMed1997

Increased hepatic beta-oxidation of docosahexaenoic acid, elongation of eicosapentaenoic acid, and acylation of lysophosphatidate in rats fed a docosahexaenoic acid-enriched diet.

Rats were fed a diet supplemented with corn oil (n-3 deficient), soy oil, or a mixture containing 8% 22:6n-3 ethyl ester for 6 wk. The hepatic capacities for the beta-oxidation and synthesis of 22:6n-3, in addition to the acylation of lysophosphatidate, were tested in vitro. In rats that were fed a 22:6n-3-enriched diet, both the beta-oxidation of 22:6n-3 and elongation of 20:5n-3 were enhanced compared to those in rats fed the other diets. Acylation of lysophosphatidate was also enhanced in rats fed a 22:6n-3-enriched diet, while the rate of dephosphorylation of phosphatidate was not changed. The amount of 22:6n-3 in the liver was much less than that consumed in a docosahexaenoic acid-enriched diet. These results suggest that a significant amount of dietary 22:6n-3 was degraded via beta-oxidation, and that a portion of the retroconverted 20:5n-3 was recycled for the synthesis of 22:6n-3. The recycling of 20:5n-3 might contribute to the low level of 22:6n-3 in rats fed an n-3-deficient diet.

Acylation↗
PubMed1981

Circular, but not circularly permuted, deoxyribonucleic acid reacts slower than linear deoxyribonucleic acid with complementary linear deoxyribonucleic acid.

The electron microscope was used to count the number of double-stranded linear and circular renaturation products of a 2:1 by weight mixture of restricted double-stranded linear phi X174 RFI and single-stranded circular phi X174 viral deoxyribonucleic acid (DNA). More linear molecules than circular molecules are observed. However, when a 1:1 mixture of aliquots of either phi X174 RFI or SV40 DNA, each previously cleaved with a different single-site restriction enzyme, is denatured and renatured under conditions which assure circularization with out of phase molecules, an equal number of linear and circular molecules is observed. These experiments indicate that the nucleation rate is not affected by circular permutation of linear strands but is decreased approximately 3-fold when one of the reacting strands is circular. An excluded volume theory is developed which is consistent with these as well as previous results concerning the effects of DNA strand lengths on renaturation rates.

Bacteriophage phi X 174↗
PubMed1986

Influence of ofloxacin, norfloxacin, nalidixic acid, pyromidic acid and pipemidic acid on human gamma-interferon production and blastogenesis.

Several new quinolone derivatives were investigated for their influence on human lymphocyte blastogenesis and gamma-interferon production following concanavalin A stimulation. All the antimicrobials induced inhibition of lymphocyte DNA synthesis. The gamma-interferon measurements showed that nalidixic acid and norfloxacin have a negative influence on lymphokine production and release.

Adult↗