PubMed Health⌕ Search

Biomedical subjects

A M Krstulovic

Publications and source records attributed to A M Krstulovic.

At least 19 recordsLinked to original sources
PubMed1989

Improved performance of the second generation alpha 1-AGP columns: applications to the routine assay of plasma levels of alfuzosin hydrochloride.

Described is a direct enantioselective separation of the enantiomers of alfuzosin hydrochloride on the second generation alpha 1-AGP column which offers improved efficiency, shorter analysis, and improved stability with respect to the first generation columns. The method has been applied to the analysis of drug substance in rat plasma. This highly efficient extraction method and the use of fluorimetric detection result in selective and sensitive determination of the enantiomers. The analytical validation parameters demonstrate the applicability of this method to pharmacokinetic and metabolic studies.

Animals↗
PubMed1979

Identification and quantitation of nucleosides, bases and other UV-absorbing compounds in serum, using reversed-phase high-performance liquid chromatography. II. Evaluation of human sera.

The reversed-phase mode of high-performance liquid chromatography was used to investigate the profiles of low-molecular-weight, UV-absorbing compounds in human serum. Identification techniques are described which allow for the identification of picomole amounts of the nucleosides, bases and other compounds in several microliters of serum ultrafiltrate. The sera from 31 normal subjects (17 males, 14 females) showed very consistent profiles. A total of 12 compounds were identified and quantified in normal serum. The analysis of sera from over 150 patients with various types of neoplasia and other diseases showed serum profiles significantly different from normal profile.

Chromatography, High Pressure Liquid↗
PubMed1979

Diagnosis of neural crest tumors by reversed-phase high-performance liquid chromatographic determination of urinary catecholamine metabolites.

Aberrations in the metabolic pathways of catecholamines in patients with neural crest tumors result in characteristic urinary excretion patterns of their catabolites. Tumors such as pheochromocytoma, neuroblastoma and ganglioneuroma usually defy clinical diagnosis because of their rarity, small size, intraabdominal position and clinical symptoms similar to those of essential hypertension. Quantitative determination of catecholamine metabolites such as vanillylmandelic acid (VMA) and 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG) offers possibilities for reliable confirmation of diagnosis. However, previous techniques for the assessment of catabolite levels suffered from inadequate sensitivity, reproducibility or specificity, which seriously diminished their usefulness as biochemical determinants in the prognosis of these life-threatening tumors. Reported in this paper is the analysis of urinary levels of VMA and MHPG using reversed-phase high-performance liquid chromatography with electrochemical and sectrophotometric detection. We present the excretion patterns showing these metabolites in 15 control subjects, 15 patients with pheochromocytoma and 5 patients with neuroblastoma.

Catecholamines↗
PubMed1979

Rapid assessment of endogenous creatinine in physiological samples analyzed by reversed-phase liquid chromatography with spectrophotometric detection.

An improved and direct analysis of endogenous creatinine levels using the reversed-phase mode of high performance liquid chromatography (RPLC) is described. The analysis is rapid, the sensitivity of the spectrophotometric detection is in the nanomole range, and the sample preparation requires only filtration to remove the particulate matter. Identification of chromatographic peaks was achieved by means of absorbance ratios, stopped-flow UV spectra and prechromatographic incubation of samples with creatinine amidohydrolase. Reported in this paper are representative chromatograms of samples of amniotic fluid, urine, and cerebrospinal fluid (CSF). The ranges of creatinine concentrations in 10 samples of amniotic fluid, urine and CSF were 0.774--1.850, 99--454.5 and 0.648--1.05 mg/100 ml, respectively. This highly specific and simple assay offers several improvements over previously used methods.

Amniotic Fluid↗
PubMed1979

Routine reversed-phase high-performance liquid chromatographic measurement of urinary vanillylmandelic acid in patients with neural crest tumors.

A rapid and simple reversed-phase high-performance liquid chromatographic procedure for the determination of vanillylmandelic acid (VMA) is described. This method was applied in the determination of the VMA content in urine from normal subjects and patients with neural crest lesions. Sample preparation is minimal and the analysis is short (20 min) and reproducible. The sensitivity of the UV detection is in the ng range. By this technique, fourteen adult control subjects were found to excrete a mean of 2.86 microgram VMA per mg creatinine, whereas twelve patients with pheochromocytoma excreted a mean of 15.7 microgram VMA per mg creatinine.

Chromatography, High Pressure Liquid↗
PubMed1979

Amniotic fluid uric acid levels determined by reversed-phase liquid chromatography with spectrophotometric and electrochemical detection.

A rapid and precise, reversed-phase high-performance liquid chromatography method for amniotic fluid uric acid is described. Detection of uric acid and other naturally occurring constitutents is based on UV absorption at a wavelength of 280 nm and direct electrochemical oxidation at a potential of +0.800 V. The total analysis time is short (20 min) and the assay requires only filtration of the samples. Uric acid levels were determined in 14 samples of amniotic fluid obtained during the 15th to 24th week of gestation. Results ranged from 0.897 to 4.39 mg per 100 ml of amniotic fluid.

Amniotic Fluid↗
PubMed1979

High performance liquid chromatographic determination of serum UV profiles of normal subjects and patients with breast cancer and benign fibrocystic changes.

High performance liquid chromatography (HPLC) was used to determine the UV profiles of serum samples taken postoperatively from 22 patients with histologically documented breast cancer, 8 patients with benign breast fibrocystic changes and 10 normal subjects. The analyses were performed on coded serum samples and after they were completed, the code was broken and the results correlated with the clinical data. Only one ml of serum was required for the HPLC analysis and identification. Detection limits for the nucleosides and bases were in the 10--20 pmol range and the injection volume of the deproteinated serum was 75 mul. The UV profiles of the normal subjects were very reproducible and similar to those of the patients with benign fibrocystic changes. The profiles of some of the cancer patients were distinctly different from the two other groups, 1-methylinosine and N2-methylguanosine, which were not detected in sera from normal subjects and patients with benign fibrocystic changes, were found in 45.5% and 22.7% of the cancer patients, respectively. Patients with the metastatic disease also showed elevated levels of guanosine and uridine. Only one false positive was found in the normal population. At present, it is not clear whether this indicates a subclinical manifestation of the disease and it must await further follow-up.

Breast Diseases↗
PubMed1979

Rapid assay for tryptophanase using reversed-phase high-performance liquid chromatography.

A rapid and sensitive high-performance liquid-chromatographic assay for tryptophanase based upon the fluorometric measurement of the enzymatically liberated indole was developed. The total incubation time is 20 min, and the reversed-phase separation is fast (elution time of indole in 8 min) and reproducible. The sensitivity of the method is in the nanomole range. This method was tested in the assay of tryptophanase activity in E. coli, giving an average activity of 6589.6 U/g of cells. Because of its speed, high sensitivity and minimal sample preparation, this method circumvents several problems commonly encountered in standard spectrophotometric methods of analysis.

Chromatography, High Pressure Liquid↗
PubMed1979

High-performance liquid chromatographic assay for acid and alkaline phosphatase in serum.

High-performance liquid chromatography was used to assay serum acid and alkaline phosphatase. Samples were incubated with adenosine-5'-monophosphoric acid (AMP) in a buffer of required pH, 5'-nucleotidase was inhibited with Ni2+ ions, and the phosphatase activity was determined by measuring the concentration of the reaction product, adenosine. The analysis time, after the incubation is terminated, is short (7 min), and the assay is quantitative and reproducible. Complete separation of the reaction product from the substrate and the naturally occurring serum constituents and the high sensitivity of the ultraviolet detection system eliminate some of the problems commonly encountered in spectrophotometric assays.

Acid Phosphatase↗
PubMed1979

Use of native fluorescence measurements and stopped-flow scanning technique in the high-performance liquid chromatographic analysis of catecholamines and related compounds.

Simultaneous separation of catecholamines and tryptophan metabolites has been carried out using a reversed-phase partition mode of high-performance liquid chromatography (HPLC). Compounds are detected and measured via their native fluorescence emitted with an excitation wavelength of 285 nm and the emission cut-off filter of 340 nm. Sample preparation is minimized and the assay is selective and well-suited for routine analyses. The sensitivity of the method is in the nanogram range. The identity of chromatographic peaks is confirmed by their excitation spectra, obtained by the stopped-flow fluorescence scanning method.

Animals↗
PubMed1979

Reversed-phase liquid chromatographic separation of 3',5'-cyclic ribonucleotides.

A rapid, reversed-phase "high-performance" liquid-chromatographic separation of the five naturally occurring cyclic ribonucleotides is described. The separation, optimized for the measurement of these compounds in biological samples, is short (25 min), sensitive (50-100 pmol), and requires no sample pre-concentration steps. We also report an alternative isocratic elution mode, optimized for a rapid and selective analysis for adenosine 3',5'-cyclic phosphate. The identity of chromatographic peaks in biological extracts is confirmed by several methods: retention times, co-chromatography with the reference compounds, absorbance ratios, enzymatic peak-shift with cyclic nucleotide phosphodiesterase, and stopped-flow ultraviolet-scanning techniques.

Animals↗