Study of catecholamines in patient urine samples by capillary electrophoresis.

Capillary zone electrophoresis with photodiode array detection at 220 nm was used for analysis of catechol compounds in human urine. The method was optimized with reference compounds 3,4-dihydroxybenzylamine, adrenaline, noradrenaline, normetanephrine, dopamine, dopac (homogensitic acid), methanephrine, vanillyl-mandelic acid, 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid and 3-methoxytyramic acid at pH 4.0 and 8.0 for their electrophoretic separation. The UV spectra of the catechols were detected at a concentration of 20 microM. Repeatability of the method calculated using the absolute migration times of the catechols was below 1.5% and using the peak areas below 5%. The patient samples were hydrolyzed by 0.5 M acid or base solutions. In the studies, a few patient samples were analyzed using 3,4-dihydroxybenzylamine as an internal standard. In the hydrolysis steps needed for their detection in urine, all the other catecholamines, except 5-HIAA, did not decompose to detectable species at 220 or 254 nm. The concentrations of the catecholamines observed in real samples were at nM levels.

Urinary 5-hydroxyindoleacetic acid (5-HIAA) excretion during multiple-day high-dose chemotherapy.

Highly emetogenic drugs such as cisplatin induce an increase in the urinary 5-hydroxyindoleacetic acid (5-HIAA) level, the main metabolite of serotonin (5-HT), within the first 24 h following a single infusion, thus providing a possible cause for acute emesis and an explanation for the action of 5-HT3 antagonists. No further excretion peaks have been observed, suggesting that additional or serotonin-independent mechanisms cause delayed emesis. Our aim was to study the mechanisms behind emesis seen during a highly emetogenic chemotherapy regimen given as a continuous infusion over several days. Seven women treated with a 4-day high-dose chemotherapy (HDCT) regimen for breast cancer entered the study. Pooled urine samples were collected prior to and during chemotherapy for determining 5-HIAA excretion. An excretion peak in the urinary 5-HIAA level was observed within the first 24 h with no further peaks thereafter. Thus, the mechanisms behind the emesis experienced during this highly emetogenic multiple-day chemotherapy regimen from days 2-3 onwards would appear to be at least partially serotonin independent and would not be expected to be completely relieved by 5-HT3 antagonists alone.

Breath acetone in congestive heart failure.

To summarize, CHF predisposes to postabsorptive ketosis in relation to the severity of venous congestion. A simple and fully noninvasive measurement of breath acetone may add to the diagnostic assessment of patients with CHF.

Two alpha-chain hemoglobin variants, Hb Broussais and Hb Cemenelum, characterized by cation-exchange HPLC, isoelectric focusing, and peptide sequencing.

We here report the characteristics of two rare alpha-chain hemoglobin (Hb) variants. The variants were found during quantification of HbA1c by cation-exchange HPLC with the Diamat glycohemoglobin analyzer. They were further characterized by isoelectric focusing and PolyCAT A cation-exchange chromatography. The structure of the abnormal Hbs was established by amino acid analysis after separation of the globin chains by reversed-phase chromatography, digestion with trypsin, separation of the peptides by reversed-phase chromatography, and amino acid sequencing. These studies showed that the two variants were Hb Broussais [alpha 90 (FG2)Lys-->Asn] and Hb Cemenelum [alpha 92 (FG4)Arg-->Trp].

Three assays for glycohemoglobin compared.

Using 123 specimens, we compared the concordance of three different methods for determining glycohemoglobin (GHb): the Diamat (Bio-Rad Laboratories), an automated analyzer measuring HbA1c by cation-exchange chromatography; an assay with the IMx analyzer (Abbott Laboratories), based on boronate affinity binding; and an HPLC method measuring HbA1c by cation-exchange chromatography on a PolyCAT A column (PolyLC Inc.). The Pearson's correlation coefficient between PolyCAT A and Diamat was 0.900 +/- 0.038 (mean +/- 2 SD) and between PolyCAT A and IMx, 0.857 +/- 0.042. However, up to twofold differences were seen in some samples. The proportion of GHb was consistently lower with the PolyCAT A method than with the other two assays, apparently because of better separation of HbA1c from nonglycated coeluting forms of Hb. The difference in glycation percentage between the PolyCAT A and Diamat methods is 2-3% over the whole concentration range. These results point to the limitations of Diamat as a reference method to be used to calibrate other methods for determining HbA1c. Further, a switch from one method to another is likely to cause considerable problems in the clinical follow-up of certain patients.

Finding the "natural" vector bases for multidimensional reference values.

The concept of reference values can be extended to multidimensional results. A probability function describes the relative density of the observations in the multivariate space. When the density of a given point is measured relative to all other points, we get an estimate of the density rank of a given point. If the rank of a point is lower than 95 per cent of all points, the multidimensional result is outside the multidimensional reference range. The single-dimensional case is a special case of this general concept. Many observations are needed to define multidimensional distributions. However, less points are needed if the dimensionality of the data matrix is reduced by statistical methods such as principal component analysis (PCA). Also other vector bases than the orthogonal solution produced by PCA are possible, and all of them compress data equally well. So the choice must be based on other criteria than compression. We propose using a vector basis that consists of positive numbers. The positive vectors can be found by direct methods such as Alternating Regression (AR) or they can be modified from the results of the PCA. Positive vectors resemble the spectra that are familiar in chemistry and physics. They are a "natural" way to describe multidimensional results. It is easier to name the positive vectors than the purely statistical vectors of PCA. To obtain a unique positive solution, additional constraints besides positivity are needed.

The pharmacokinetics and pharmacodynamics of doxazosin compared with atenolol during long-term double-blind treatment.

The pharmacodynamics of doxazosin and atenolol were compared on single study days in 39 patients with mild to moderate hypertension receiving long-term double-blind treatment. The pharmacokinetics of doxazosin were investigated in the 20 patients receiving doxazosin. Individually titrated once daily doses of doxazosin were 1, 2, 4, 8 or 16 mg and of atenolol 50 or 100 mg. Patients were first investigated after at least one month on constant dose and then again after at least a further three months. Mean plasma concentrations of doxazosin were proportional to dose and the plasma half-life was 11.5 h and independent of dose. There was low variability of doxazosin plasma concentrations between patients receiving the same dose. Concentrations and half-life were unchanged during the period between investigations. Mean reductions of AUC (0-12 h) blood pressure during the 12-h period post-dose and of blood pressure at 24 h post-dose were not statistically different between doxazosin and atenolol. There was effective control of blood pressure by both drugs at all time points of the day. The pharmacokinetic and pharmacodynamic results obtained in this study are compatible with the use of doxazosin in a once daily dose regimen for the treatment of essential hypertension.

Analysis of external quality assessment results in three dimensions.

During the last six years there has been a marked change in the nature of interlaboratory variance in enzyme determinations in Finland. With ordinary two-dimensional plotting methods the change is difficult to see, because enzyme activities are different for each control serum. The decrease in the coefficient of variation (CV) is best seen when the CV is displayed as a trend surface as a function of time and enzyme activity. While the overall variance has decreased, the shape of the curve relating CV to enzyme activity has also changed. The dependence of CV on the enzyme activity level has decreased slightly. The use of trend surfaces to describe three-dimensional functions in external quality assessment is described.