Biomedical subjects

N Rujikarn

Publications and source records attributed to N Rujikarn.

4 recordsLinked to original sources

PubMed1991

Isocratic high-performance liquid chromatography-photodiode-array detection method for determination of lysine- and arginine-vasopressins and oxytocin in biological samples.

A simple, isocratic, sensitive (1 ng), and specific high-performance liquid chromatographic (HPLC) method based on photodiode-array detection (PAD) is described for simultaneous quantitation of the bioactive peptides, lysine vasopressin (LVP), arginine vasopressin (AVP) and oxytocin (OXY). Acidified pig plasma and left ventricular (LV) tissue samples were first extracted with Sep-Pak C18 columns, and the bioactive peptides were eluted with methanol, then dried at 37 degrees C and reconstituted with HPLC mobile phase. The bioactive peptides were separated by HPLC on a Dynamax 3009-A C8 column with a mobile phase of 0.1% trichloroacetic acid-50 mM heptanesulfonic acid-30mM triethylamine-20% acetonitrile in water, pH 2.5 and identified with a Waters 990-PAD system (spectrum index plots in the range 200-400 nm). Standards of LVP, AVP and OXY and their mixtures showed a linear increase in the range 5 to 100 ng and were eluted at 6.1, 6.9 and 4.6 min, respectively. Spectrum analysis showed a distinct absorption peak at 280 nm, corresponding to peptide bonds. The reproducibility of the method coefficient of variation for standards is 6.9, 5.8 and 4.7% for LVP, AVP and OXY, respectively. In plasma and tissue it is much higher: 12.9% (LV tissue) and 18.6% (plasma) for LVP. Pig plasma contains negligible amounts of AVP and OXY; LVP is much higher (0.28 +/- 0.19 ng/ml). In pig tissue, LVP predominates (6.95 ng/g wet weight) compared to AVP (1.45) and OXY (1.50). Spectral analysis is necessary to identify the bioactive peptide peaks among interfering substances and to increase the sensitivity four-fold. The method described here is useful for the simultaneous determination of LVP, AVP and OXY in the nanogram range and can be extended to picogram levels by employing PAD spectral analysis techniques.

Animals↗

PubMed1990

Effect of oxygen free radicals and lipid peroxides on cardiac isoenzymes.

We report here the effect of oxygen free radicals, OFR (superoxide, O2-; hydroxy, OH; t-butylhydroperoxide, H2O2) lipid peroxides (malondialdehyde, MDA), free radical scavengers (superoxide dismutase, catalase, allopurinol) and generator (ferrous chloride) antioxidants (ascorbate, glutathione) spin traps (5,5-dimethyl-1-pyroline-N-oxide, N-t-butyl-L-pheny nitrone) on the cardiac isoenzyme (CK, CK-MB, LDH, LD1) concentrations in the sera of patients with acute myocardial infarction. CK-MB and LD1 were rapidly and completely inactivated by O2- (50 nmol/ml), OH (1 nmol/ml) and MDA (0.6 microM). Butylhydroperoxide (600 microM), and ferrous chloride (200 microM) selectively inhibited CK-MB. The free radical scavengers, antioxidants and spin traps all had minimal effects, and H2O2 had none.

Antioxidants↗

PubMed1989

Taurine lowers blood pressure in the spontaneously hypertensive rat by a catecholamine independent mechanism.

Taurine, a sulfur aminoacid, has been studied for a role in blood pressure regulation since it functions as a generalized inhibitory neurotransmitter and is found in high concentrations in the myocardium. We reinvestigated the magnitude of the hypotensive effect of chronic taurine administration to the spontaneously hypertensive rat (SHR) and the role of catecholamines in such an action. The SHR received either a 1% taurine solution or tap water to drink for 16 weeks. Taurine treatment caused a significant persistent reduction in blood pressure by 4 weeks that was maximal at 16 weeks (146 +/- 6 [exp.] v 182 +/- 5 [control] mm Hg, P less than .01). While this taurine-induced decline in blood pressure in the SHR was not accompanied by alterations in plasma epinephrine levels, there was a steady 235% increment in the norepinephrine concentration from 231 +/- 31 pg/mL initially to 542 +/- 126 pg/mL at completion of the study, P less than .02. The reduction in blood pressure was associated with decreased proteinuria in the taurine-treated SHR (9.6 +/- 4 [exp.] v 21.5 +/- 7 [control] mg/24 h, P less than .02) and less cardiac and renal hypertrophy. We conclude that taurine administration results in a 20 to 25% reduction in blood pressure in the SHR. The mechanism of this hypotensive action requires further study but is independent of changes in plasma catecholamine levels. The vasodepressor effect of taurine leads to less hypertensive injury to the kidney and heart in the SHR.

Animals↗

PubMed1988

High-performance liquid chromatographic method for the direct quantitation of oxy radicals in myocardium and blood by means of 1,3-dimethylthiourea and dimethyl sulfoxide.

A direct, sensitive (50-200 ng), simple and specific high-performance liquid chromatographic (HPLC) method is described for the quantitation of oxy radicals by means of the consumption of dimethyl sulfoxide (DMSO) by the hydroxy radical and dimethylthiourea (DMTU) by hydrogen peroxide. The specific scavengers catalase and L-methionine were used to quantitate hydrogen peroxide and OH, respectively. The DMSO and DMTU peaks were separated and identified by HPLC on a Waters C18 Resolve 10-microns Radial-Pak column with an isocratic mobile phase (5% aqueous methanol) at 2 ml/min with UV detection (DMSO, 214 nm; DMTU, 240 nm). The OH concentrations were extrapolated by a luminol chemiluminescence technique. A linear relationship was obtained for DMTU consumption by hydrogen peroxide in the range 0.25-0.40 mM with a coefficient of variation (C.V.) of 8.8 +/- 2.1% and for DMSO consumption by hydroxy radicals in the range 0.1-3.2 microM OH, with a C.V. of 9.6 +/- 3.6%. The limits of detection for this method were 50 ng of hydrogen peroxide for DMTU and 200 ng of OH for DMSO. Hydrogen peroxide averaged 10.5 +/- 3.6 nmol/ml in blood and 56.4 +/- 5.3 mumol/g wet weight in left ventricular (LV) tissue. The hydroxy radical concentration was 0.1 microM in blood and 0.3 microM in LV tissue.

Animals↗