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At least 1,765 records · Page 98Linked to original sources
PubMed2002

Minimal number of chromatographic test parameters for the characterisation of reversed-phase liquid chromatographic stationary phases.

This paper focuses on the classification or differentiation of RP-HPLC columns based on measured chromatographic properties. A chemometric study has been conducted on a published data set consisting of 85 RP-HPLC columns and on a data set consisting of 47 self-tested columns. Principal component analysis enables determination of the number of parameters necessary for a rational differentiation. The results show that reducing the number of parameters for such differentiation still allows classification of the columns just as a higher number did. It is shown that three test parameters produce a classification similar to that obtained with five parameters.

Chromatography, High Pressure Liquid↗
PubMed2000

Analysis of tetrahydro-beta-carboline-3-carboxylic acids in foods by solid-phase extraction and reversed-phase high-performance liquid chromatography combined with fluorescence detection.

The presence and analysis of two tetrahydro-beta-carboline-3-carboxylic acids in foods are studied. Sample preparation with benzenesulfonic acid strong cation-exchange columns followed by RP-HPLC-fluorescence allowed a reliable analysis and spectral characterization of 1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid (THCA) and 1-methyl-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid (MTCA). Experimental data showed that upon oxidation tetrahydro-beta-carboline-3-carboxylic acids gave rise to beta-carbolines (norharman and harman) that were also chromatographically separated and their fluorescent profile monitored. This approach was useful to confirm identification of tetrahydro-beta-carboline-3-carboxylic acids in foods. Several foods and beverages contained THCA and MTCA in varying proportions. Their occurrence in foods implies that diet is a source of these compounds in humans.

Carbolines↗
PubMed1998

Randomised trial of management of hypertensive pregnancies by Korotkoff phase IV or phase V.

BACKGROUND: There is debate about whether diastolic blood pressure should be recorded as the fourth (muffling, K4) or fifth (disappearance, K5) Korotkoff sound in pregnancy. We compared maternal and fetal outcomes and the likelihood that episodes of severe hypertension would be recorded when hypertensive pregnancies were managed according to either K4 or K5. METHODS: 220 pregnant women with diastolic hypertension (K4 > or =90 mm Hg) after the 20th week of gestation were enrolled in a prospective randomised study at two obstetric units in Australia; they were randomly assigned management with K4 (n=103) or K5 (n=117) for the remainder of the pregnancy. Clinical management was according to a uniform department protocol. Analysis was by intention to treat. All the women completed the trial. FINDINGS: An episode of severe hypertension (systolic > or =170 mm Hg, diastolic > or =110 mm Hg, or both) was more likely to be recorded with use of K4 than with use of K5 (39 [38%] vs 30 [26%] women, p=0.051), mainly because of a greater likelihood that severe diastolic hypertension would be recorded (34 [33%] vs 20 [17%], p=0.006). The frequency of severe systolic hypertension and simultaneous severe systolic and diastolic hypertension did not differ between groups. Pregnancy was prolonged by an average of 2 weeks in both groups, and there were no significant differences between the groups in laboratory data, requirements for antihypertensive treatment, birthweight, fetal growth retardation, or perinatal mortality. There was no eclampsia or significant maternal morbidity in either group. INTERPRETATION: A change from use of K4 to K5 would mean that one fewer case of severe diastolic hypertension would be recorded for every six hypertensive pregnancies, but all other episodes of severe hypertension would be recorded with similar frequency. Since the K4/K5 difference is smaller in hypertensive than in normotensive pregnant women and since K5 is closer to the actual intra-arterial pressure and more reliably detected, universal adoption of K5 to record diastolic blood pressure in hypertensive pregnancy should be considered.

Blood Pressure Determination↗
PubMed1991

The influence of "essential" phospholipids (EPL) on phase-I- and phase-II-reactions and on the glutathione status in the liver of aging rats.

"Essential" phospholipids (EPL; polyene-phosphatidylcholine) were administered orally to aging male rats in doses of 100 and 300 mg/kg b.wt. over 10 weeks. One and 7 days after the last treatment cytochrome P-450 concentration, epoxide hydrolase and glutathione-S-transferases were found to be unchanged, but ethylmorphine N-demethylation, ethoxycoumarin O-deethylation and UDP-glucuronosyltransferase activities were enhanced, as were the concentrations of both reduced and oxidized glutathione, the values being similar to those in young adult rats. These results are discussed in terms of an increase in endoplasmic reticulum membrane fluidity.

7-Alkoxycoumarin O-Dealkylase↗
PubMed1997

Metanil yellow: a bifunctional inducer of hepatic phase I and phase II xenobiotic-metabolizing enzymes.

Metanil yellow, a non-permitted food colour, has been found in various foodstuffs. The induction potential of metanil yellow on hepatic microsomal cytochrome P-450 (P-450)-dependent monooxygenases and cytosolic detoxification enzymes, namely, glutathione S-transferase (GST) and quinone reductase (QR), was investigated. Oral administration of metanil yellow (430 mg/kg body weight) to four animals for seven days caused significant induction of hepatic P-450 (48%) and its dependent aryl hydrocarbon hydroxylase (100%) activity and cytosolic GST (136%) and QR (92%) activities. Parenteral administration of metanil yellow (80 mg/kg body weight) to another set of four animals for 3 days resulted in higher induction of ethoxyresorufin-O-deethylase (228%) as compared to other monooxygenases (64-92%), while GST and QR were also found to be induced (59-95%). Spectra of metanil yellow-induced microsomes showed an increase in P-450 with a shift of 2.2 nm in the soret region. The results suggest that metanil yellow acts as a bifunctional inducer of specific isozymes of P-450 and cytosolic enzymes and thus may involve the cytosolic aryl hydrocarbon (Ah) receptor for this type of induction.

Administration, Oral↗
PubMed1996

Effect of dietary protein on hepatic and extrahepatic phase I and phase II drug metabolizing enzymes.

Weanling male rats were fed low (LP, 7.5%), standard (SP, 15%) or high protein (HP, 45%) diet for 7 or 14 days ad libitum, and cytochrome c reductase (CYC) and UDP-glucuronosyltransferase (UGT) enzyme activities were determined in intestine, kidney and liver microsomes. HP diet increased CYC activity in intestine and kidney, while LP diet had no effect. Hepatic CYC activity declined with decreasing level of dietary protein. Liver and intestine UGT activities were higher on an LP diet, while kidney enzyme activities were higher on an HP diet. UGT activity toward alpha-naphthol, a UGT1 isoform substrate, was modulated by dietary protein in all tissues, while UGT activity toward 4-hydroxybiphenyl, a substrate for a second UGT1 isoform, was affected only in the intestine. The duration of feeding affected CYC and UGT activities in the intestine. This observation may be explained by the dynamic nature of intestinal tissue. The observation of unique tissue and enzyme responses suggests that generalizations regarding metabolic response to diets based on hepatic studies or single enzymes, may be erroneous.

Animals↗
PubMed1988

Isolation of basic drugs from plasma using solid-phase extraction with a cyanopropyl-bonded phase.

The use of a CN sorbent for the isolation of basic compounds from plasma is described. Adsorption from water and plasma was investigated for a test set of 30 basic drugs. It was found that compounds with a carbon chain length greater than or equal to 11 are totally retained and that the competitive effect of the matrix on the adsorption is minimal. Methanol-phosphate buffer (pH 3, mu = 0.05) (50:50) yielded good recoveries for more polar compounds; apolar basic drugs can be efficiently eluted using methanol containing 0.1% propylamine. Water up to 3 ml can be used for the washing step. This approach was applied to the determination of eight drugs in plasma at therapeutic levels. The absolute recoveries (n = 6) obtained were 98.8 +/- 7.3% for papaverine, 82.3 +/- 3.9% for practolol, 83.4 +/- 2.6% for metoclopramide, 87.3 +/- 5.8% for imipramine, 82.8 +/- 3.3% for procaine, 82.7 +/- 4.6% for morphine, 87.5 +/- 7.2% for propranolol and 90.4 +/- 6.2% for yohimbine.

Adsorption↗