Label-free silver triangular nanoplates for spectrophotometric determination of catecholamines and their metabolites

A novel method towards spectrophotometric determination of catecholamines and their metabolites differing in their functional groups has been developed. This method is based on a change in morphology of silver triangular nanoplates upon the action of cateсholamines and their metabolites, which is manifested by the decrease of the nanoparticle local surface plasmon resonance (LSPR) band intensity or its shift to the short-wavelength region of the spectrum. The shift value of the LSPR band or the change of its intensity increases with increasing concentration of catecholamines or their metabolites, which is proposed for their spectrophotometric determination. The limits of detection of catecholamines and their metabolites under selected conditions increase in the series homovanillic acid < vanillylmandelic acid < L-epinephrine < L-norepinephrine < dopamine and are 0.25, 1.2, 3.0, 64, and 130 μmol L^-1, respectively. The selectivity of the proposed method was assessed using vanillylmandelic acid as example. It was found that the determination of vanillylmandelic acid does is not interfered in the presence of 4000-fold excess of Na⁺, K⁺, CH₃COO^-, and 1000-fold excess of Mg²⁺, Ca²⁺, Al³⁺, NO₃^-. The method also allows for the selective determination of vanillylmandelic acid in the presence of a 1000-fold excess of structurally related substances that do not contain either a catechol fragment or an electron donor substituent. The proposed approach was successfully applied to the determination of catecholamines in pharmaceuticals and artificial urine. Graphical abstract.

Specific Urinary Metabolites in Malignant Melanoma

Background and objectives: Melanin, which has a confirmed role in melanoma cell behaviour, is formed in the process of melanogenesis and is synthesized from tryptophan, L-tyrosine and their metabolites. All these metabolites are easily detectable by chromatography in urine. Materials and Methods: Urine samples of 133 individuals (82 malignant melanoma patients and 51 healthy controls) were analysed by reversed-phase high-performance liquid chromatography (RP-HPLC). The diagnosis of malignant melanoma was confirmed histologically. Results: Chromatograms of melanoma patients showed increased levels of 5,6-dihydroxyindole-2-carboxylic acid, vanilmandelic acid, homovanilic acid, tryptophan, 5-hydroxyindole-3-acetic acid, and indoxyl sulphate compared to healthy controls. Concentration of indoxyl sulphate, homovanilic acid and tryptophan were significantly increased even in the low clinical stage 0 of the disease (indoxyl sulphate, homovanilic acid and tryptophan in patients with clinical stage 0 vs. controls expressed as medium/ interquartile range in µmol/mmol creatinine: 28.37/15.30 vs. 5.00/6.91; 47.97/33.08 vs. 7.33/21.25; and 16.38/15.98 vs. 3.46/6.22, respectively). Conclusions: HPLC detection of metabolites of L-tyrosine and tryptophan in the urine of melanoma patients may play a significant role in diagnostics as well as a therapeutic strategy of melanoma cancer.

Development of a gas chromatography silicon-based microsystem in clinical diagnostics

The accurate determination of biological parameters by means of rapid, on-line measurements at low-concentrations is an important task within the fields of pharmaceutical screening and medical diagnostic. Nevertheless, in biological samples, the analytes of interest are present as minor components in complex mixtures and with interfering species. Biosensors are the best candidates for these applications providing a direct solution to this need of accuracy, but their intrinsic selectivity often excludes all the other components in the sample. A separation step introduced prior to the sensing component could allow both the increase of selectivity with respect the interfering species and the identification of a large spectrum of molecular components in the sample. This work reports the development of a silicon-based integrated separation microsystem for gas chromatography aimed to biomedical applications, with particular emphasis to monitor the homovanillic acid (HVA) and vanillylmandelic acid (VMA) ratios in mass population screening for neuroblastoma diagnosis and prognosis. The miniaturised system consists of two main modules: (i) a metal oxide semiconductor detector and (ii) a micromachined separation capillary column. As first step, the metal oxide semiconductor capability to detect HVA and VMA has been demonstrated. Then, a technology for a silicon separation capillary microcolumn including the on-chip gas sensor housing has been proposed and a first prototype has been developed. The proposed microsystem is an analytical device with biosensing capabilities for diagnostic and biomedical applications, which yield an electronic signal proportional to the concentration of a specific analyte or group of analytes.

Comparative values of catecholamines and metabolites for the diagnosis of neuroblastoma

In order to diagnose neuroblastomas, we assayed the three adrenal hormones and five of their metabolites by high-performance liquid chromatography followed by electrochemical detection in urine samples of 395 children with tumours of unknown nature (including 29 neuroblastomas). The analytes (expressed as analyte/creatinine ratios) performances were determined by calculating the related sensitivity and specificity and receiver operating characteristics curves within the different age groups. Normetanephrine (NME), vanillylmandelic and homovanillic acids (VMA, HVA) were the best analytes. Calculated optimal thresholds (best specificity/sensitivity couples) of these analytes minimised the number of false-positive diagnosis.

CONCLUSION

combined determination of normetanephrine with vanillylmandelic acid (0-1 year) or homovanillic acid (1-5 years and 5-10 years) further enhanced the diagnostic power up to 100% sensitivity and specificity of the testing depending on the age group. Plotting individual levels (normetanephrine versus vanillylmandelic acid or homovanillic acid) allowed a rapid visual analysis that would have missed only one small low grade non-secreting tumour.

Voltammetric sensor for vanillylmandelic acid based on molecularly imprinted polymer-modified electrodes

Despite the increasing number of applications of molecularly imprinted polymers (MIPs) in analytical chemistry, the construction of a biomimetic voltammetric sensor remains still challenging. This work investigates the development of a voltammetric sensor for vanillylmandelic acid (VMA) based on acrylic MIP-modified electrodes. Thin layers of MIPs for VMA have been prepared by spin coating the surface of a glassy carbon electrode with the monomers mixture (template, methacrylic acid, a cross-linking agent and solvent), followed by in situ photopolymerisation. After extraction of the template molecule, the peak current recorded with the imprinted sensor after rebinding was linear with VMA concentration in the range 19-350 microg ml(-1), whereas the response of the control electrode is independent of incubation concentration, and was about one-tenth of the value recorded with the imprinted sensor at the maximum concentration tested. Under the conditions used, the sensor is able to differentiate between VMA and other closely structural-related compounds, such as 3-methoxy-4-hydroxyphenylethylene glycol (not detected), or 3,4- and 2,5-dihydroxyphenilacetic acids, which are adsorbed on the bare electrode surface but not at the polymer layer. Homovanillic acid was detected with the imprinted sensors after incubation, indicating that the presence of both methoxy and carboxylic groups in the same position as in VMA is necessary for effective binding in the imprinted sites. Nevertheless, both species can be differentiated by the oxidation potential. It can be concluded that MIP-based voltammetric electrodes are very promising analytical tool for the development of highly selective analytical sensors.

[Biochemical diagnosis of pheochromocytoma and neuroblastomas]

Pheochromocytoma and neuroblastoma are distinct tumours, but their biological diagnosis is based on secretion increase of one or several catecholamines. Assays have to be very sensible and specific for an early diagnosis. 24 hours urinary catecholamines and metabolites are currently measured, but technical improvements permit plasma metanephrine assay, an excellent indicator of pheochromocytoma. HPLC coupled to electrochemical detection represents the most efficient methodology. After a review of urinary and plasma assay methods, the authors show usual values of catecholamines, metanephrines, HVA and VMA, according to ages, and give examples of results encountered in classical or not tumours and in falsely positive cases. Urinary metanephrine assay is the most sensible and specific in biological diagnosis of pheochromocytoma, while catecholamines and VMA assays lack of sensibility. Results have to be given by 24 hours and by creatinine ratio. Metanephrine assay can be performed also in plasma and exhibits the same interest. However, in urine as in plasma, in case of renal failure, results cannot be interpreted. Neuroblastoma biological diagnosis is based classically on HVA, VMA, and dopamine assays, nowadays only in 24 hours urine (or in urinary micturition for screening), and results are also expressed as creatinine ratio. But even if several assays are advisable, 5% of the neuroblastoma cases do not produce increased catecholamine values. In some cases, metanephrine assay could be of interest. After the age of 12 months, clinical expression of neuroblastoma is dramatic in 70% of cases. So, a biological screening has been experimented in several countries including France. A French translation of the consensus conference report (1998) is appended, which shows the complexity of neuroblastoma screening. Now, there is no evidence that early tumour detection by screening lessens the mortality rate, but a weak benefit is not excluded.

Adrenergic hyperactivity and metanephrine excess in the nucleus accumbens after prefrontocortical dopamine depletion

Selective dopamine depletion within the medial prefrontal cortex in rats is known to enhance dopamine and norepinephrine levels in the nucleus accumbens and to induce characteristic behavioral disturbances. The present study was designed to determine levels of adrenaline, apart from dopamine and norepinephrine, and metabolites in the nucleus accumbens after prefrontocortical dopamine depletion. Prefrontocortical dopamine depletion was carried out by injecting 6-hydroxydopamine, and it was validated through: the emergence of behavioral disturbances such as amphetamine-induced stereotypies, spontaneous motor hyperactivity, and enhanced "anxiety-like" responses and through postmortem quantification of catecholamine levels by using high-performance liquid chromatography. The findings indicated that lesioned rats exhibited more oral stereotypies after amphetamine, were hyperlocomotive, and showed more pronounced anxiety-like behaviors than controls. Following prefrontocortical dopamine depletion, postmortem concentrations of dopamine and norepinephrine, along with the metabolites 3,4-dihydroxyphenylacetic acid and vanillylmandelic acid, were reliably enhanced in the nucleus accumbens as expected, and dopamine turnover was decreased. Furthermore the nucleus accumbens contained higher levels of adrenaline and its transmethylated metabolite metanephrine. To sum up, prefrontocortical dopamine depletion induces motor and emotional disturbances in rats and alters the neurochemical profile of the nucleus accumbens, not only inducing dopaminergic and noradrenergic hyperactivity but also leading to adrenaline and metanephrine excess.

Evaluation of catecholamine metabolites, mIBG scan, and bone marrow cytology as response markers in stage 4 neuroblastoma

BACKGROUND

The early biological response has been proved an excellent predictor in acute lymphoblastic leukemia and nephroblastoma. We asked whether catecholamine metabolites, mIBG scan, and bone marrow evaluation might be relevant response markers in disseminated neuroblastoma.

PROCEDURE

Three hundred sixty-seven unselected stage 4 neuroblastoma patients treated according the German cooperative trial NB90 were entered into the study. Catecholamine plasma and urine levels were centrally determined by gas chromatography/ mass spectrometry. Bone marrow cytology and mIBG scans were evaluated by local investigators.

RESULTS

At diagnosis, mIBG scan was positive in 306 patients (92%), borderline in seven patients (2%), and negative in 19 patients (6%). Bone marrow aspirates were cytologically positive in 292 patients (84%) and negative in 57 patients (16%). Plasma catecholamine levels were elevated in 79% (206 of 260 patients.), urinary levels in 91% (307 of 338 patients). The outcome of patients with normalized mIBG scan after four courses of chemotherapy [5 year EFS (event free survival) 0.22 +/- 0.07] was not superior to the outcome of patients with still abnormal uptake (5 year EFS 0.30 +/- 0.05). The event free survival of patients with still positive bone marrow aspirates after four courses (0.16 +/- 0.06) was inferior to the EFS of patients with negative bone marrow aspirates (0.26 +/- 0.04, P = 0.0054). Urinary catecholamine normalization after four cycles of chemotherapy (5 year EFS 0.35 +/- 0.06 versus 0.26 +/- 0.10) had no influence on outcome, whereas plasma catecholamine normalization after the first (5 year EFS 0.40 +/- 0.09 versus 0.14 +/- 0.07, P= 0.0364) or the fourth cycle (5 year EFS 0.35 +/- 0.06 versus 0.26 +/- 0.10, P = 0.0242) indicated a better outcome.

CONCLUSIONS

These data show that serial plasma catecholamine levels and bone marrow aspirates in the course of the disease are useful tools in predicting outcome.

A 5-year (1990-1994) neuroblastoma screening feasibility study in France. Methodology and preliminary observations

INTRODUCTION

Following the pioneering Japanese experience, several European and North American groups implemented pilot studies on screening infants for neuroblastoma, considering the possibility of demonstrating a decrease in mortality rate. In France, a 5-year (1990-1994) feasibility study on neuroblastoma screening at the age of 4 months was initiated in the Rhône district (1.5 M inhabitants, 26,000 births per year).

METHODS

Vanillylmandelic (VMA) and homovanillic (HVA) acids were measured by HPLC, and creatinine (Cr) by the Jaffé's kinetic method on Technicon RA-XT. VMA and HVA were expressed as microgram/mg of Cr. The method was assessed with both a daily intra-laboratory control and a sample of urine obtained from a national quality control organism.

RESULTS AND DISCUSSION

The overall participation rate for the 5-year period was 82.2%. Out of 105,293 infants tested from 128,126 births, 12 NB cases were discovered with screening (screened cases) and 1 case was discovered with a late performed test (at 13 months of age). Six neuroblastomas were found clinically before the age of 4 m. Two cases were missed because the parents did not perform the test. Three children with normal tests at screening were false-negative cases: two of them were found secreting at diagnosis, while one remained non-secretory at diagnosis and later on. Otherwise, thirty-five false-positive tests were found. Biochemical observations are discussed. It is too early to reach clinical conclusions from this screening program on neuroblastomas as it is presently being followed up.

The influence of total sleep deprivation on urinary excretion of catecholamine metabolites in major depression

To elucidate the influence of total sleep deprivation (TSD) on catecholaminergic neurotransmission, which is assumed to be disturbed in depression, 9 depressive patients collected consecutive 24-h urine samples prior to (baseline), during (TSD) and following total sleep deprivation (post-TSD). Urine samples were analysed for total MHPG (3-methoxy-4-hydroxyphenylglycol), conjugates of MHPG (glucuronide and sulfate), excretion of HVA (homovanillic acid) and VMA (3-methoxy-4-hydroxymandelic acid). TSD increased the urinary excretion of MHPG-sulfate as a marker of the central norepinephrine metabolism and the excretion rates of VMA and HVA as indices of the peripheral catecholamine metabolism. Patients with higher VMA values prior to TSD reacted worse, and the VMA increase due to TSD was positively correlated with the response. The results demonstrate that TSD, besides acting as a stimulus on the peripheral sympathetic nervous system, influences central nervous noradrenergic neurotransmission, as reflected by the increase of MHPG-sulfate.

Effects of N-ethyl,N-nitrosourea on monoamine concentrations and metabolizing enzymes in mouse brain regions

N-ethyl,N-nitrosourea is a well known alkylating agent and produces central nervous system-specific tumors in several laboratory animal species. In the present study, young male CD-1 mice were treated by i.p. injections of 0, 2, 8, or 32 mg/kg body weight N-ethyl,N-nitrosourea, twice a week for 3 weeks. Endogenous levels of brain monoamine neurotransmitters and their selected metabolites; norepinephrine (NE), dopamine (DA), 5-hydroxytryptamine (5-HT), vanillylmandelic acid (VMA), dihydroxyphenyl acetic acid (dopac), homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA), and dihydroxyphenylalanine (dopa) were measured using HPLC with electrochemical detection. N-ethyl,N-nitrosourea treatment caused an increase of NE and 5-HT in the hypothalamus and striatum. Increased levels of 5-HIAA were noticed in the same brain regions. Elevated levels of NE were also observed in the cerebral cortex, medulla oblongata and the cerebellum. The major metabolite of NE, VMA, was decreased in several brain regions to non-detectable levels. Histopathological examination of brain tissue did not reveal any pathologic lesions. The increases in brain amines were associated with increased activity of tryptophan hydroxylase in the hypothalamus and corpus striatum. Dopa-decarboxylase was elevated in the cerebral cortex at a low dose of N-ethyl,N-nitrosourea only, whereas the monoamine oxidase activity was unaltered. Results indicated that N-ethyl,N-nitrosourea exposure may cause an elevation of steady state levels of various biogenic amines in brain areas and these changes to some extent are consistent with the altered activity of metabolizing enzymes.

[Development of a liquid chromatography/multiple electrochemical detector (LCMC) and its application in neuroscience]

A liquid chromatographic system with multiple electrochemical detectors (LCMC) was newly developed for quantitating 20 to 30 neurochemicals simultaneously within 20 to 25 min from one sample derived from biological specimens. The device can be used for estimating neurofunctional changes in the central nervous system under the influence of CNS drugs, behavioral changes of experimental animals and psychic effects in clinical stages, etc. The system consists of four parallel liquid chromatographs with multiple electrochemical detectors. The first three systems determine catecholamines, indoleamines and related compounds. The fourth system is for measuring acetylcholine and choline with an internal standard. A new type of electrochemical detector was developed that consists of 4 electrodes set at a different potentials: each of the eluting components was identified by the variation of 4 current peaks on each electrode. Twenty-eight standard compounds, including four internal standards, could be clearly separated; and the detection limits of these compounds were at least 0.1 to 0.4 pmol per injection. In this report, the usefulness and applicability of this system were confirmed by measuring neurochemicals in the striatum of rats sacrificed either by decapitation or microwave irradiation and in the human ventricular cerebrospinal fluid of patients with Parkinson's disease and essential tremor.

Determination of monoamines and indoles in amniotic fluid by high-performance liquid chromatography-electrochemical detection

A technique is presented for the separation and detection in amniotic fluid of various substances associated with catecholamine metabolism. Monoamines and their metabolites were separated using reversed-phase ion-pair high-performance liquid chromatography. Detection and quantification were performed electrochemically. The retention times of 28 standards associated with the monoamines and their precursors and metabolites were evaluated with 14 different eluents. On the basis of the retention times of each standard and the modification of the retention times of the various peaks detected in amniotic fluid, the following substances were identified in this biological fluid: 4-hydroxy-3-methoxyphenylacetic acid, 5-hydroxyindoleacetic acid, 3,4-dihydroxyphenylacetic acid, 4-hydroxy-3-methoxyphenylglycol, epinephrine, 4-hydroxy-3-methoxymandelic acid, octopamine, tyrosine and tryptophan.

N-myc oncogene and stage IV-S neuroblastoma. Preliminary observations on ten cases

We studied the clinical significance of genomic amplification of N-myc in Stage IV-S neuroblastoma, with reference to spontaneous regression. Among 103 neuroblastomas in which N-myc was measured, ten were Stage IV-S (eight children were younger than and two were older than 1 year of age). The number of copies of N-myc was 1 to 3 in five patients, four to ten in one patient, and more than ten in four patients, and the survivors of each group were four, one, and one (recurrent), respectively. Of 41 patients younger than 1 year of age, N-myc amplification of more than three copies was found only in Stage IV-S neuroblastoma. Cure with a tendency to regress spontaneously was seen in five of eight patients younger than 1 year of age. However, two patients older than 1 year of age classified as Stage IV-S (one with N-myc amplification) died of progressive disease. In two patients (1 and 3 months of age) with a huge hepatic involvement and in whom the tumor had an amplified N-myc of more than ten copies, tumor regression occurred but there was a relapse to a progressive state later. The overexpression of N-myc mRNA occurred in nine of ten stage IV-S tumors and did not correlate with the prognosis. The vanillylmandelic acid (VMA) to homovanillic acid (HVA) ratio was low in tumors with an increased number of copies of N-myc. Serum lactate dehydrogenase (LDH) levels were increased in Stage IV-S patients with N-myc amplification but not in those with regressing tumors and without N-myc amplification. These data suggest that N-myc amplification may affect the final outcome in the patient classified as Stage IV-S, but tumor regression can occur early after birth and appears to be independent of N-myc amplification.

Amniotic fluid catecholamine metabolites in maternal smoking

The concentration of dopamine (DA), norepinephrine (NE), and its metabolites 3-methoxy-4-hydroxy-phenylethylene glycol (MHPG) and vanillyl mandelic acid (VMA), and prostaglandins E2, and F2a in amniotic fluid were measured at labor (1-3 cm of cervical dilatation), in uncomplicated and complicated pregnancies. The amniotic fluid concentration (mean +/- SD) of MHPG in maternal smoking (S) (30.6 +/- 11.9 nmol.mg creatinine-1) and intrauterine growth retardation (IUGR) (36.7 +/- 15.2 nmol.mg creatinine-1) groups is significantly higher than in uncomplicated pregnancies (C) (22.9 +/- 8.8 nmol.mg creatinine-1), or diabetes mellitus groups (D) (26.1 +/- 10.9 nmol.mg creatinine-1) groups; VMA presents similar differences between groups S (145.8 +/- 84.4 nmol.mg creatinine-1) and IUGR (173.0 +/- 135.4 nmol.mg creatinine-1) higher than C (58.3 +/- 26.1 nmol.mg creatinine-1) and D (76.8 +/- 49.0 nmol.mg creatinine-1) groups. NE levels differ between groups in a similar way, but DA does not present significant differences between groups. Prostaglandin levels are higher in the S than in the C group. Nicotine action and/or hypoxia are proposed as a possible cause of NE, MHPG, and VMA rise in amniotic fluid of S, and IUGR versus C or D groups.

Unconjugated methoxylated catecholamine metabolites in human saliva. Quantitation methodology and comparison with plasma levels

A newly developed method for the simultaneous extraction and quantitation of the unconjugated levels of the catecholamine metabolites vanilmandelic acid (VMA), 3-methoxy-4-hydroxyphenylethylene glycol (MHPG) and homovanillic acid (HVA) in plasma by high performance liquid chromatography with electrochemical detection was modified and applied to studies of human saliva. The assay had a mean coefficient of variation under 3% for each of the metabolites. Levels of plasma VMA, MHPG and HVA were measured in 28 normal subjects and compared to their saliva levels, obtained before and after stimulation by mastication. Significant correlations were found between plasma and saliva MHPG and HVA, but there was no correlation between plasma and saliva VMA. Salivary MHPG and HVA can be reproducibly assayed and may be useful tools for indications of changes in central and peripheral catecholamine metabolism.

Norepinephrine and its metabolites in cerebrospinal fluid, plasma, and urine. Relationship to hypothalamic-pituitary-adrenal axis function in depression

Among 140 depressed and control subjects, there were significant positive correlations between indexes of noradrenergic activity in cerebrospinal fluid (CSF), plasma, and urine. Among the depressed patients, CSF levels of the norepinephrine (NE) metabolite 3-methoxy-4-hydroxyphenylglycol (MHPG) and urinary outputs of NE and its metabolites normetanephrine, MHPG, and vanillylmandelic acid correlated significantly with plasma cortisol levels in relation to dexamethasone administration. Also, CSF levels of MHPG were significantly higher among patients who were cortisol nonsuppressors than among either patients who were cortisol suppressors or controls. Urinary outputs of NE and normetanephrine were significantly higher among patients who were cortisol nonsuppressors than among controls. Patients who were cortisol suppressors had indexes of NE metabolism similar to those of controls. These results in the depressed patients extend recent observations suggesting that dysregulation of the noradrenergic system and hypothalamic-pituitary-adrenal axis occur together in a subgroup of depressed patients.

Malignant pheochromocytoma: effective treatment with a combination of cyclophosphamide, vincristine, and dacarbazine

STUDY OBJECTIVE

To determine the efficacy and toxicity of combination chemotherapy in patients with advanced, malignant pheochromocytoma.

DESIGN

Nonrandomized, single-arm trial.

SETTING

Governmental medical referral center.

PATIENTS

Fourteen patients with malignant pheochromocytoma confirmed by histologic tests. All patients had metastatic disease and elevated urinary catecholamine secretion.

INTERVENTIONS

After optimization of antihypertensive therapy, patients received cyclophosphamide, 750 mg/m2 body surface area on day 1; vincristine, 1.4 mg/m2 on day 1, and dacarbazine, 600 mg/m2 on days 1 and 2, every 21 days.

MEASUREMENTS AND MAIN RESULTS

Combination chemotherapy with cyclophosphamide, vincristine, and dacarbazine produced a complete and partial response rate of 57% (median duration, 21 months; range, 7 to more than 34). Complete and partial biochemical responses were seen in 79% of patients (median duration, more than 22 months; range, 6 to more than 35). All responding patients had objective improvement in performance status and blood pressure. Toxicity included expected hematologic, neurologic, and gastrointestinal effects of chemotherapy without serious sequelae. There were four minor hypotensive episodes and one minor hypertensive episode.

CONCLUSIONS

Combination chemotherapy with cyclophosphamide, vincristine, and dacarbazine is effective for advanced malignant pheochromocytoma. Urinary catecholamines are useful to ascertain biochemical response to therapy.

Liquid-chromatographic measurement of catecholamines and metabolites in plasma and urine

In this general method for measuring the concentrations of neurotransmitters in body fluids by "high performance" liquid chromatography (HPLC), the procedures for extracting different biogenic amines from body fluids vary, but the basic chromatographic conditions are the same for all. We use citric/formic acid buffer as the mobile phase, a C18 column, and an electrochemical detector. Specificity is better than in previously reported methods. Because of its excellent cost efficiency, we consider this to be the method of choice for quantifying biogenic amines.

A fluorometric high performance liquid chromatographic assay for vanillylmandelic acid (VMA) developed from a commercial kit method

A fluorometric procedure based on the Bio-Rad Vanillylmandelic Acid (VMA) by High Performance Liquid Chromatography (HPLC) Test was developed. Detection by fluorescence provides better sensitivity and specificity than the Pisano spectrophotometric method. Use of a C18 mini-column extraction to extract VMA prior to HPLC analysis significantly reduced the late eluting peaks. A linear range was established up to 400 mumol/L of VMA. Within-run and between-run CV's were 3.0% and 3.7%, respectively. In a comparison of this fluorometric method with the Pisano spectrophotometric method, a linear regression of y = 0.807x + 2.185 was obtained with a correlation coefficient of 0.945. In the analysis of over 50 samples, no intereferences have been found.

Sensitive determination of tyrosine metabolites, p-hydroxyphenylacetic acid, 4-hydroxy-3-methoxyphenyl-acetic acid and 4-hydroxy-3-methoxymandelic acid, by gas chromatography-negative-ion chemical-ionization mass spectrometry. Application to a stable isotope-labelled tracer experiment to investigate their metabolism in man

A method has been established for studying the dynamic metabolism of tyrosine to its metabolites in humans using a deuterium-labelled amino acid. Phenylalanine-d5 was administered orally to human subjects (5 mg/kg) and the levels of p-hydroxyphenylacetic acid-d4, 4-hydroxy-3-methoxyphenylacetic acid-d3, and 4-hydroxy-3-methoxymandelic acid-d3 excreted into urine every hour were determined by gas chromatography-negative-ion chemical-ionization mass spectrometry. This method was also applied to some patients with depression and it was possible to detect a slight alteration in the excretion of some compounds compared with the control.

Primary carcinoid tumor of urinary bladder

Invasive carcinoid tumor of the urinary bladder in a sixty-five-year-old man who presented with painless gross hematuria was documented by light and electron microscopic studies. The presence of 5-hydroxyindoleacetic acid (5-HIAA) and absence of vanillylmandelic acid (VMA) was determined in the neoplastic tissue by chemical analysis. This was consistent with the findings of elevated 5-HIAA and normal VMA in the twenty-four-hour urine sample. Sections of the tumor yielded negative argentaffin and argyrophil reactions. The relevant literature is reviewed.

High-performance liquid chromatographic assay of free norepinephrine, epinephrine, dopamine, vanillylmandelic acid and homovanillic acid

A procedure is described for the concurrent assay of free norepinephrine, epinephrine, dopamine, vanillylmandelic acid and homovanillic acid in physiological fluids using high-performance liquid chromatography with electrochemical detection. The column packing is an octadecyl-bonded silica. A single mobile phase containing 1-octanesulphonate is used for the assay of catecholamines and for the assay of the acidic metabolites. An efficient sample preparation scheme is presented for the isolation of the catecholamines and their acidic metabolites from the same sample aliquot. Catecholamines are extracted by ion exchange on small columns and adsorption on alumina, using dihydroxybenzylamine as an internal standard. Vanillylmandelic acid and homovanillic acid are recovered from the combined loading and washing effluents of the ion-exchange column by a solvent extraction procedure. Recovery of catecholamines averages 67%. The limit of detection for individual catecholamines is ca. 30 pg. Recoveries of vanillylmandelic acid and homovanillic acid average 77% and 87%, respectively. The use of the same mobile phase for the concurrent assay of catecholamines and their acidic metabolites considerably increases the throughput of samples in the chromatographic system by eliminating the time-consuming column-equilibration periods.

Sensitive mass fragmentographic determination of acidic catecholamine metabolites in human body fluids

A sensitive and simple method for the simultaneous quantitation of homovanillic acid and vanilmandelic acid in small samples (0.1-1.0 ml) of urine, serum, plasma and cerebrospinal fluid is described. The stable dimethylthiophosphinyl methyl ester derivatives are detected specifically by mass fragmentography using the respective deuterated compounds as internal standards. Gas chromatographic separation is performed on a fused-silica DB-1 capillary column combined with a cold injection system for large sample volumes. Linear response curves and a detection limit of 1 ng/ml are obtained. The method has been applied to the localization of pheochromocytoma by selective determination of venous vanilmandelic acid.

Neuroendocrinoma of the jejunum: electron microscopic and biochemical analysis

A 56-year-old woman presented with a sudden, severe hemorrhage per rectum. Angiography localized a jejunal tumor, which was excised. Light microscopy suggested a neuroendocrine tumor, but neither a smooth muscle tumor nor a lymphoma could be excluded. Electron microscopy showed dense cored, single membrane bound secretory granules 150--220 nm in diameter; myofilaments were not observed. Biochemical analysis of tumor tissue yielded considerable amounts of catecholamines. VMA, 5-HIAA, and metanephrines. These combined ultrastructural and biochemical observations establish the diagnosis of neuroendocrine tumor; however, in this case neither type of information is sufficiently specific to define the tumor as either a paraganglioma or a carcinoid. Although paraganglia and mucosal endocrine cells in the GI are currently thought to constitute distinct cell types, they share numerous structural and functional properties, and they are both thought to be part of the APUD cell system. These parallels and similarities are shared by the neoplasms derived from them which often display features of both. In the absence of specific granule types or specific substances isolated from tumor tissue, only the application of specific immunocytochemistry techniques may allow the precise "functional" classification of such tumors.

Catecholamine metabolites in amniotic fluid as indicators of intrauterine stress

The catecholamine metabolites HMPG and VMA have been determined in samples of amniotic fluid in 38 uncomplicated pregnancies, seven cases of IUGR, and six cases of diabetes. A successive increase of HMPG and VMA was found toward the end of the pregnancy. HMPG and particularly the HMPG/VMA ratio were significantly higher in the amniotic fluid of the growth-retarded fetuses than in the uncomplicated cases. No significant difference was found between the diabetic and uncomplicated cases.

[Modern methods in localization of pheochromocytomas (author's transl)]

In six patients with adrenal pheochromocytoma the tumors were localized by ultrasonography, phlebography of the adrenal glands and by estimation of plasma catecholamines selectively obtained from the vena cava and the adrenal gland veins. All tumors were localized by selective catecholamine estimation, five by ultrasonography, and four by phlebography. The smallest pheochromocytoma of 1.5 g weight was only localized by selective catecholamine estimation but not by ultrasonography or phlebography. This tumor, however, had been visualized by computed tomography. To avoid diagnostic errors by selective catecholamine estimation, it is important to withdraw blood from the adrenal gland veins prior to the injection of any radiographic contrast media, since this may result in an extremely enhanced secretion of catecholamines from the adrenal medulla.

Mass-fragmentographic determination of catecholamine metabolites in amniotic fluid and its possible clinical usefulness

We describe the determination of 3-methoxy-4-hydroxy-phenylacetic acid, 3-methoxy-4-hydroxyphenylamandelic acid, and 3-methoxy-4-hydroxyphenylethylene glycol in amniotic fluid by means of mass fragmentography, with use of deuterated internal standards. The results expressed in terms of absolute concentration and creatinine concentration, are given as a function of gestational age. In the 15th to 17th week, concentrations in amniotic fluid are a reflection of those in the mother's serum, whereas in the 32nd to 40th week, these concentrations, expressed in terms of creatinine, are similar to those found in the urine of newborns. We discuss the possible usefulness of the determination of catecholamine metabolites in amniotic fluid in the diagnosis of congenital neuroblastoma, maternal pheochromocytoma, and underdevelopment.

Hypercalcitoninaemia in patients with pheochromocytoma

As pheochromocytoma sometimes is accompanied by medullary thyroid carcinoma (in the sense of multiple endocrine adonomatosis type II = Sipple-Syndrome), serum calcitonin (CT) was measured by radioimmunoassay in 4 patients with pheochromocytoma. Before extirpation of the adreno-medullary tumor, serum CT was distinctly increased to 3 and 30 ng/ml in 2 of 4 patients, respectively. After removal of the tumor, serum CT was normal in the patients and pentagastrin stimulation produced no exaggerated CT response. In hydrochloric acid extracts from the two corresponding pheochromocytoma tissues, immunoreactive-Calcitonin (IR-CT) was detected, the concentrations amounting 1 and 4 ng/mg wet tissue. These findings suggest that hypercalcitonism in patients with pheochromocytoma cannot always be ascribed to the thyroid, i.e. increased calcitonin levels do not necessarily indicate a medullary carcinoma of this organ.

Ultrastructural and biochemical analysis of "undifferentiated" pulmonary carcinomas

Seven cases of "undifferentiated" pulmonary carcinoma were studied ultrastructurally; five were of the typical oat cell variety and the remaining two consisted of larger cells. In three of the former and both of the latter cases neurosecretory-like granules were demonstrated. Biochemical analysis of tumor tissue extracts revealed 5-hydroxy-3-indoleacetic acid, vanilylmandelic acid, and catecholamine activity in all instances. No hormonal syndrome or metabolic abnormality was detected in any of the patients. The concomitant morphologic demonstration of neurosecretory-like granules and the presence of 5-hydroxy-3-indoleacetic acid, vanilylmandelic acid, and catecholamines in neoplastic tissue would provide further evidence that these tumors may indeed arise from bronchial endocrine cells and could therefore be classified within the group of neuroendocrine carcinomas. Also it seems apparent that these neuroendocrine bronchial carcinomas may include tumors consisting of cells somewhat larger than the typical oat cell. The observation of 5-hydroxy-3-indoleacetic acid, vanilylmandelic acid, and catecholamine activity in two oat cell carcinomas in which neurosecretory granules could not be demonstrated poses an interesting problem whose solution may only derive from further studies.

A radiotracer method for the measurement of central nervous system catecholamines in vivo

A new strategy for measurement of brain catecholamines was tested in an animal model. [3H]Norepinephrine was infused intravenously in rabbits to label the peripheral norepinephrine pools. The specific activity of urinary 3-methoxy-4-hydroxymandelic acid was consistently higher than that for 3-methoxy-4-hydroxyphenyglycol (MHPG). Central sympathectomy with 6-hydroxydopamine abolished this difference. Using the formula we propose, it is estimated that 30-50% of urinary MHPG originates from the central nervous system.

Catecholamine metabolites in the aqueous of retinoblastoma

The aqueous humor of five patients with histologically proven retinoblastoma were analyzed for the main catabolic products of norephinephrine and epinephrine. In each case, there were no detectable levels of normethanephrine, metanephrine, vanilmandelic acid (VMA), and 3-methoxy, 4-hydroxy phenoglycol. The techniques are sensitive to 1 microgram/ml but will not detect the presence of homovanillic acid (HVA).

Mass fragmentographic determination of vanilmandelic acid, homovanillic acid and isohomovanillic acid in human body fluids

Vanilmandelic, homovanillic and isohomovanillic acids in body fluids were efficiently isolated by liquid chromatography on an Amberlite XAD-4 column and by organic extraction in a special apparatus. The purified metabolites were converted into their trifluoroacetylhexafluroisopropanol esters and analyzed by mass fragmentography. The working curves of the metabolites were linear from 0.5 to 5 ng injected. The minimum detectable concentrations of all the metabolites were 2 ng/ml for plasma and cerebrospinal fluid, and 120 ng/ml for urine. The metabolite concentrations in plasma, cerebrospinal fluid and urine of normal persons and patients were determined.

Recent developments in the clinical assessment of the metabolism of aromatics by high-performance, reversed-phase chromatography with amperometric detection

High-performance liquid chromatography with electrochemical detection has developed into a tool with excellent capability to monitor picomole amounts of individual metabolites in both tissue and body-fluid specimens. Significant technical advances in the area of microparticle chemically-bonded stationary phases have led to dramatic improvements in both sensitivity and resolution. Reversed-phase systems can be modified to include charged exchange sites by addition of detergents to the mobile phase. Adjustment of the surface charge in this manner permits capacity factors for ionic sample components to be increased or decreased. This concept is quite compatible with electrochemical detection and has provided the foundation for several clinical assays now in routine use. Examples of additional applications are presented for the determination of catecholamines in tissue, 3-methoxy-4-hydroxyphenylglycol in urine, and dopamine-beta-hydroxylase activity in human serum.

Malignant gastric neuroendogrinomas. Ultrastructural and biochemical characterization of their secretory activity

In two cases of malignant gastric tumors originally diagnosed as undifferentiated carcinomas electron microscopy revealed a neurosecretory type of granule. Subsequently tumor extracts were tested by biochemical methods and shown to have vanillylmandelic acid and 5-hydroxy-3-indoleacetic acid activity. Neither patient had signs or symptoms referable to the presence of these or related substances. These observations parallel those made in a variety of neuroendocrine tumors in which demonstration of neurosecretory granules or isolation of amine or peptide materials or their metabolites has not necessarily been reflected in clinical hormonal syndromes. Our findings indicate that regardless of clinically apparent hormonal activity or lack thereof, some undifferentiated gastric carcinomas may in fact derive from neuroendocrine APUD elements.

Biochemical post-mortem findings in depressed patients

Biochemical human post-mortem studies on depressed patients indicate an unspecific deficiency of neurotransmitters in several brain areas. The loss of drive of these patients could be correlated with a decrease of striatal dopamine concentration. Noradrenaline was significantly diminished in red nucleus, a fact which points to the characteristic posture of depressed patients. Serotonin was diminished in all brain areas. During remission all values trended to be normal. There also exists a circadian disrhythm in depressed patients resulting in lowered VMA- and HVA-levels in urines during the morning and a remission to normal values in the evening. This agrees with the findings of lowered blood tyrosine levels in the morning. The ratio of blood tyrosine and tryptophan is disturbed during depression and recovers during remission. Central and peripheral biochemical mechanisms seems to be involved in depression syndrom.

Neurohumoral mechanisms in hypertension

Neurohumoral mechanisms operating via the catecholamines are discussed in their relationship to such hypertensive diseases as pheochromocytoma and labile and established essential hypertension. 2. In pheochromocytoma, diagnosis depends almost entirely on identification of increased amounts of catecholamine metabolites in the urine. Because of the danger, manipulative or invasive procedures both for diagnosis and during surgery should be kept at a minimum. 3. In established essential hypertension, reactivity to norepinephrine and plasma norepinephrine are increased, whereas norepinephrine uptake and apparent secretion rate are decreased. 4. In labile essential hypertension, reactivity to epinephrine and probably plasma epinephrine are increased and uptake of epinephrine decreased. 5. Labile hypertension with all its characteristics may or may not coexist with established essential hypertension with all its features. 6. The sympathetic nervous system is also involved in other types of hypertensive disease. Many patients with renovascular hypertension as well as with primary and secondary hyperaldosteronism also have essential hypertension. Angiotensin II affects the sympathetic nervous system and the juxtaglomerular apparatus appears to be beta adrenergic receptor activated, at least in part.