Coating proteins: structure and cross-linking in fp-1 from the green shell mussel Perna canaliculus

The protein family known as fp-1 provides mussel byssus with a protective outer coating and has drawn much attention for its water resistant bioadhesive properties in vitro. A new fp-l isolated from the green shell mussel Perna canaliculus (pcfp-1) reveals a composition dominated by only four amino acids: 3,4-dihydroxyphenyl-L-alanine (dopa), lysine, proline, and valine at approximately 20 mol % each. SDS-PAGE and MALDI-TOF mass spectrometry detected size variants at 48 and 52 kDa in preparations of purified Pcfp-1. The N-terminal sequence enabled construction of oligonucleotide primers for PCR and RACE-derived cDNAs from which the complete sequence of four variants was deduced. pcfp-1 deviates from all known homologues in other mussels in several notable respects: its mass is half, most of its sequence is represented by 75 tandem repeats of a tetrapeptide, i.e., PY*VK, in which Y* is dopa, prolines are not hydroxylated, and thiolate cysteines are clustered in homologous sequences at both the amino and carboxy termini. Amino acids in the repeat sequence show a striking resemblance to proline-rich cell wall proteins with tandemly repeated PPVYK pentapeptides [Hong, J. C., Nagao, R. T., and Key, J. L. (1987) J. Biol. Chem. 262, 8367-8376]. Cysteine plays a key role in cross-linking pcfp-1 by forming adducts with dopaquinone. Significant 5-S-cysteinyldopa and smaller amounts of 2-S-cysteinyldopa were detected in hydrolysates of the byssal threads of P. canaliculus. The cross-links could also be formed by oxidation of pcfp-1 in vitro using mushroom tyrosinase. Cysteinyldopa cross-links were present in trace amounts only in the byssus of other mussel species.

[5-S-cysteinyldopa as a tumor marker for primary uveal malignant melanoma]

The clinical significance of 5-S-cysteinyldopa (5-S-CD), a major intermediate in melanin synthesis, was evaluated as a potential diagnostic tumor marker for uveal melanoma. Serum concentrations of 5-S-CD in 6 out of 7 patients with uveal melanoma in the absence of extraocular metastases were close to those of controls. In contrast, serum concentrations of 5-S-CD were found to be elevated in 3 patients with systemic metastases of melanoma. In addition, 5-S-CD in intraocular fluids, including both aqueous and vitreous humor, was elevated in patients with uveal melanoma regardless of the presence or absence of systemic metastases. These results suggest that 5-S-CD in the intraocular fluid may serve as a useful biochemical marker for the diagnosis of uveal melanoma.

[Amines and pteridines]

Polyamines (putrescine, spermidine and spermine) play important roles in cell proliferation and differentiation, and have been established as tumors markers. We and other workers have confirmed that N1-acetylspermidine in tumor tissues, spermidine and spermine in erythrocytes, and N1,N12-diacetylspermine in urine might be the most sensitive indicators for various forms of tumors. Neopterin is a marker of cell-mediated immunostimulation, and may be a helpful marker in monitoring cancer patients. HPLC and immunological assays of neopterin, biopterin, and N2-(3-aminopropyl)biopterin(oncopterin) in urine might be useful in the clinical study of pteridines, as cancer markers. Serum 5-S-cysteinyldopa level is a useful and specific biochemical marker for malignant melanoma.

Sensitive high-performance liquid chromatographic method for the determination of 5-S-cysteinyldopamine, 5-S-cysteinyl-3,4-dihydroxyphenylacetic acid and 5-S-cysteinyl-3,4-dihydroxyphenylalanine

A new HPLC method for the determination of 5-S-cysteinylcatechols has been developed. The alumina adsorbed fraction of the supernatant of brain homogenate was injected onto a reversed-phase column and a citrate-phosphate buffer containing 1-nonyl sulphate was used as mobile phase (pH 2.1). Two dual-series working electrodes of a thin-layer cell were operating together, joined by a special coupler. The assay allows determination of the 5-S-cysteinylcatechols in the striatum, limbic system and mesencephalon of one guinea pig. Recoveries of the three 5-S-cysteinylcatechols were 59-76%, whereas the limit of quantitation was 0.04-0.10 pmol. The coefficient of variation was less than 0.76-1.10% and linearity was found up to a concentration of 500 pmol. By adding ascorbic acid to the samples, artifacts resulting in HPLC peaks were either reduced in size or deleted.

Melanins in IGR 1 melanoma cells

Information on the composition of melanins is obtained by analysis both of 4-amino-3-hydroxyphenylalanine (AHP) after hydriodic acid degradation and of pyrrole-2,3,5-tricarboxylic acid (PTCA) after potassium permanganate oxidation. Analysis of thiazole-4,5-dicarboxylic acid (TDCA) and pyrrole-2,3-dicarboxylic acid (PDCA) after permanganate oxidation, provides additional information on the composition, TDCA on pheomelanin residues, and PDCA on indolic residues without carboxy groups. Using model melanins formed from dopa and cysteinyldopa in different proportions, we found the TDCA/(PTCA+PDCA) ratio to yield a reliable estimate of the relative proportions of pheomelanin and eumelanin. The PDCA/PTCA ratio reflects the relationship between indole residues with and without carboxy groups. We have analyzed degradation products from cultures of IGR 1, an extensively studied melanoma cell line. Cell cultures were harvested after 2, 4, and 7 days. Culture media were changed after 2 days in all series, and also after 4 days in one series harvested at 7 days. Cells without medium change had seven times the amount of melanin found in cultures with medium change. The PDCA/PTCA ratio decreased with increasing amounts of melanin. With increased melanization, eumelanin is increased relatively more than pheomelanin. The cell content of 5-S-cysteinyldopa (5-S-CD) was similar in all cultures, while 6-hydroxy-5-methoxyindole-2-carboxylic acid (6H5MICA), a eumelanin precursor metabolite, was found in increased amounts of media of heavily pigmented cultures.

Melanins in IGR 1 melanoma cells

Information on the composition of melanins is obtained by analysis both of 4-amino-3-hydroxyphenylalanine (AHP) after hydriodic acid degradation and of pyrrole-2,3,5-tricarboxylic acid (PTCA) after potassium permanganate oxidation. Analysis of thiazole-4,5-dicarboxylic acid (TDCA) and pyrrole-2,3-dicarboxylic acid (PDCA) after permanganate oxidation, provides additional information on the composition, TDCA on pheomelanin residues, and PDCA on indolic residues without carboxy groups. Using model melanins formed from dopa and cysteinyldopa in different proportions, we found the TDCA/(PTCA+PDCA) ratio to yield a reliable estimate of the relative proportions of pheomelanin and eumelanin. The PDCA/PTCA ratio reflects the relationship between indole residues with and without carboxy groups. We have analyzed degradation products from cultures of IGR 1, an extensively studied melanoma cell line. Cell cultures were harvested after 2, 4, and 7 days. Culture media were changed after 2 days in all series, and also after 4 days in one series harvested at 7 days. Cells without medium change had seven times the amount of melanin found in cultures with medium change. The PDCA/PTCA ratio decreased with increasing amounts of melanin. With increased melanization, eumelanin is increased relatively more than pheomelanin. The cell content of 5-S-cysteinyldopa (5-S-CD) was similar in all cultures, while 6-hydroxy-5-methoxyindole-2-carboxylic acid (6H5MICA), a eumelanin precursor metabolite, was found in increased amounts of media of heavily pigmented cultures.

Evaluation of melanin-related metabolites as markers of melanoma progression

BACKGROUND

Urinary excretion of 5-S-cysteinyldopa (5-S-CD) has been used as a biochemical marker of melanoma progression. Melanomas produce not only 5-S-CD but also 5,6-dihydroxyindole-2-carboxylic acid (5,6DHI2C) as major intermediates in melanin formation. 5,6DHI2C is then metabolized to the two O-methyl derivatives, 5H6MI2C and 6H5MI2C. The aim of this study was to determine which marker in serum and urine most sensitively reflected the progression of melanoma.

METHODS

Serum and 24-hour urine samples were collected and assayed serially by high-performance liquid chromatography every 1 to 4 months in 28 patients with primary or recurrent melanomas, for up to 48 months.

RESULTS

Serum concentration and urinary excretion of 5-S-CD and 6H5MI2C in patients with melanoma without metastases were close to those obtained from normal subjects. Metastases developed in 9 of the 28 patients. In seven of these nine patients, serum or urinary 5-S-CD values were elevated before or at the time of clinical detection of visceral metastases. However, serum 5-S-CD was elevated significantly earlier and reflected melanoma progression better than the physical examination and/or laboratory tests, such as scintigraphy and echography. Serum 6H5MI2C values exceeded the normal range shortly before death in three patients, and urinary 6H5MI2C did not increase at any stage in most patients, therefore these metabolites did not reflect progression of disease.

CONCLUSIONS

Among the four markers, serum 5-S-CD appears to be the best biochemical marker for the detection of progression of melanotic melanoma, a value of more than 10 nmol/l suggesting the presence of metastasis.

Serum 5-S-cysteinyldopa (5-S-CD) as a marker of melanoma progression

We previously reported that serum 5-S-cysteinyldopa (5-S-CD) tended to elevate earlier and reflect melanoma progression better than urinary 5-S-CD. In patients without metastatic melanomas, serum concentration and urinary excretion of 5-S-CD and 6-hydroxy-5-methoxy-indole-2-carboxylic acid (6H5MI2C) were within the upper limits of normal controls. In this report, we presented more precisely the changes in these melanin-related markers and clinical courses of four melanoma patients. Serum and 24-hour urine samples were serially collected and assayed every 1 to 4 months. Three of them developed stage IV malignant melanomas and died of metastatic disease. 6H5MI2C in serum and urine did not reflect the progression of disease. Among the 4 parameters considered, 5-S-CD in serum appeared to be the best biochemical marker for melanoma progression. Serum 5-S-CD over the upper limit of 10 nmol/L was suggested as a serious sign of the progression of melanoma.

5-S-cysteinyldopa in urine and tumors

1) The urinary 5-S-CD contents in malignant melanoma subjects (n = 135) and non-melanoma subjects (n = 204) were measured by HPLC. These results suggest that, as a biochemical marker, periodic measurement of urinary 5-S-CD is quite useful for evaluating the determinations of stage classification (UICC, 1987), and the detection of metastases, the therapeutic efficacy of operation or immunochemotherapy against malignant melanoma. 2) Quantitative analyses of 5-S-CD values in tissues from primary malignant melanoma lesions (n = 24) and pigmentary tumors other than melanomas (n = 136) showed 80.6-821.4 ng/mg and N.D.-55.0 ng/mg respectively. In view of the above findings, it was suggested that the pigmentary tumors can be diagnosed as malignant melanoma if the 5-S-CD value in the tissues is higher than 100 ng/mg.

[Pigmented spindle cell nevus and pigmented Spitz nevus--clinical and histopathological study on pigmented Spitz nevus, and its differentiation from early melanoma by fluorescence method and measurement of 5-S-CD level in the lesion]

On the basis of clinical and histopathological studies on 17 patients who had been diagnosed as having pigmented Spitz nevus (PSN), pigmented spindle cell nevus (PSCN) was surmised to be a type of pigmented Spitz nevus. In order to distinguish pigmented spindle cell nevus and pigmented Spitz nevus from early melanoma, 5 PSCN cases and 12 PSN cases were analyzed by the fine-needle aspiration fluorescence method, touch fluorescence method and measurement of the 5-S-CD level in the lesion. With the touch fluorescence method, fluorescent tumor cells were detected in one case of PSN. With the fine-needle aspiration fluorescence method, fluorescent tumor cells were detected in one PSCN case and 2 PSN cases. In comparison with fluorescent melanoma cells, the detected fluorescent tumor cells were smaller in size and number and resembled melanocytes. The 5-S-CD level in the lesion was 50 ng/mg or less in all cases, whereas the level in melanoma is known to be a high 100 ng/mg or more. In the final analysis, measurement of the 5-S-CD level in the lesion was concluded to have the greatest utility for differential diagnosis of pigmented spindle cell nevus and pigmented Spitz nevus from early melanoma.

An improved HPLC-electrochemical detection method for measuring brain levels of 5-S-cysteinyldopamine, 5-S-cysteinyl-3,4-dihydroxyphenylalanine, and 5-S-cysteinyl-3,4-dihydroxyphenylacetic acid

Brain levels of the 5-S-cysteinyl adducts of 3,4-dihydroxyphenylalanine (DOPA), 3,4-dihydroxyphenylacetic acid (DOPAC), and dopamine were determined in several mammalian species. The low levels of the compounds and the risk of artifacts during sample preparation necessitated rather profound modifications of the assaying method. The refined method has made it possible to present more accurate data than those previously reported from this laboratory. The occurrence of low levels of the 5-S-cysteinyl adducts in dopamine-rich brain areas, but not in cerebellum, is indirect evidence of in vivo autoxidation of DOPA, DOPAC, and dopamine. The products generated during catechol autoxidation, including quinones and reduced forms of oxygen, are known to be potentially cytotoxic.

[Definitive diagnosis of early malignant melanoma lesions by the quantitative analysis of 5-S-cysteinyldopa in the tissue and touch fluorescence method]

Methods for making diagnoses of early lesions of malignant melanomas using a touch-fluorescence method from the cut surface of the lesions and quantitative analysis of 5-S-CD in the tissues were developed. 1) The touch-fluorescence method and analyses of 5-S-CD values in the tissues were extremely useful in making definitive diagnoses of early lesions of nodular melanoma (NM). 2) Only quantitative analyses of 5-S-CD values in the tissues were useful in making definitive diagnoses of early lesions of superficial spreading melanoma (SSM). 3) It is impossible to definitively diagnose lentigo maligna using either way mentioned above. From these results, it appears that quantitative analysis of 5-S-CD values in the tissue was the most useful method for making definitive diagnoses in case of early lesions of NM and SSM.

[Biochemical diagnoses of malignant melanomas with determinations of 5-S-cysteinyldopa in lesions]

To develop a biochemical diagnosis for malignant melanomas, 5-S-cysteinyldopa in the tissues of malignant melanomas and other pigmented tumors were quantitatively analysed. The mean 5-S-CD value from primary melanotic melanoma lesions was 202.4 ng/mg (80.6-821.4) and those of metastatic melanoma lesions was 214.0 ng/mg (96.2-520.0). There was no significant differences in these 5-S-CD values between the types of primary lesions. On the other hand, the 5-S-CD values from pigmented tumors other than melanomas, such as Spitz nevus, dysplastic nevus, pigmented basal cell epithelioma, and melanoepithelioma Bloch II were less than 55 ng/mg. From these results it is thought that pigmented tumors can be diagnosed as malignant melanomas, if the 5-S-CD values in the tissues are over 100 ng/mg. The mean 5-S-CD values of pigmented macules of SSM was 734.5 ng/mg (320.0-1666.3) and those of ALM was 1.8 ng/mg (0.7-3.6). These data suggest that the biochemical diagnoses of SSM in situ can be based on 5-S-CD values, the diagnoses of ALM in situ can not.

UVB-induced melanocyte proliferation and 5-S-cysteinyldopa excretion in dysplastic nevus syndrome

This is the first in vivo study of the effects of UV on the epidermal melanocytes in dysplastic nevus syndrome (DNS). Eleven DNS patients and 22 healthy subjects were given total body UVB irradiation 8 times during 17 days and the melanocyte population was estimated in biopsies from shielded and irradiated skin. There was a doubling of the melanocyte counts in irradiated skin and a less pronounced but significant increase in the shielded skin area. The urinary excretion of 5-S-cysteinyldopa (5-S-CD) was measured before, during and after the irradiation period. The 5-S-CD excretion reached a maximum after 2 weeks of irradiation and returned towards the basal value after the irradiation period. We were not able to document any abnormal melanocytic UV response in DNS patients before, during or after the irradiation.

Identification of 5-S-cysteinyldopa by high performance liquid chromatography in biopsies from patients with dysplastic melanocytic nevi

The appearance of 5-[(L)-S-cysteinyl]dopa, a major product in pheomelanogenesis was examined in affected and nonaffected skins from 20 patients with clinical signs of dysplastic melanocytic nevi. Analysis by high performance liquid chromatography and electrochemical detection showed that 20 of the 35 lesions had a pathological formation of 5-[(L)-S-cysteinyl]dopa (0.04-28.86 ng/micrograms acid soluble protein). 5-[(L)-S-cysteinyl]dopa was not detected in any of the normal uninvolved skin samples analyzed.

Occurrence and distribution of 5-S-cysteinyl derivatives of dopamine, dopa and dopac in the brains of eight mammalian species

The 5-S-cysteinyl derivatives of dopamine, dopa (3,4-dihydroxyphenylalanine) and dopac (3,4-dihydroxyphenylacetic acid) were synthesized and used as reference compounds in high performance liquid chromatography analyses of extracts from various brain regions of eight mammalian species. All three metabolites were detected in the brains of all the species studied. The regional distribution of the metabolites was similar to that of dopamine; the metabolite concentrations ranged from less than 0.1 percent to more than 1 percent of the dopamine level, the highest ratios generally being found in substantia nigra. It is suggested that the 5-S-cysteinyl catechol metabolites have been formed after autoxidation of catechols to quinones and subsequent coupling to glutathione. The adduct thus formed is finally split by peptidases to yield the 5-S-cysteinyl derivatives.

A pulse radiolysis investigation of the oxidation of the melanin precursors 3,4-dihydroxyphenylalanine (dopa) and the cysteinyldopas

The unstable quinones of 3,4-dihydroxyphenylalanine (dopa) and the most abundant cysteinyldopa isomers (2S-, 5S- and 2,5S,S'-) have been generated rapidly via disproportionation of their respective semiquinones prepared pulse radiolytically by one-electron oxidation of the corresponding dopas with azide radicals. Dopaquinone decays via a base-catalysed unimolecular cyclisation yielding leucodopachrome which, under the present conditions, is immediately oxidised by remaining dopaquinone to form dopachrome and dopa back again. Addition of cysteine increased the rate of dopaquinone decay and precluded dopachrome formation. By contrast, the cysteinyldopa quinones decayed via an acid-catalysed unimolecular cyclisation involving the cysteine side chain to form a cyclic quinone-imine observed directly for the first time. These quinone-imine intermediates subsequently rearranged to more stable phenolic benzothiazine isomers. The addition of cysteine had little effect on cysteinyldopa quinone decay and did not prevent quinone-imine formation. The absorption spectra, extinction coefficients and rate constants for formation and decay of these various transient species involved in melanisation are reported.

Detection of 5-S-cysteinyldopamine in human brain

5-S-Cysteinyldopamine was synthesized and used as reference compound in HPLC analyses of extracts from various regions of human brain. The compound could be detected in brain regions rich in dopamine (caudate nucleus, putamen, globus pallidus and substantia nigra) but not in other regions (cerebellum, occipital cortex). The occurrence of 5-S-cysteinyldopamine in dopaminergic brain regions supports the hypothesis that dopamine in part undergoes autoxidation, leading to formation of highly reactive quinones. The newly discovered metabolite may prove useful in future studies of dopamine autoxidation and the possibly resultant cytotoxicity in aging and degenerative brain disorders.

Characterization of melanogenesis in mouse and guinea pig hair by chemical analysis of melanins and of free and bound dopa and 5-S-cysteinyldopa

This study examined how various genotypes of coat color in mice and guinea pigs are related to the type and content of melanin and to the levels of free and protein-bound dopa and 5-S-cysteinyldopa in hair. In analysis of black, yellow, and white areas of tortoiseshell guinea pigs, the melanogenesis type was in parallel to the type and content of melanin and was correlated fairly well with the levels of melanin precursors. In mouse hair, substitution of the brown allele (bb) for black (BB) reduced the eumelanin content to 1/2 to 1/3, while it significantly increased the dopa level. The dilution (dd) gene of mice reduced the eumelanin content only slightly, while the gene for pink-eyed dilution (pp) reduced the content of eumelanin and the level of dopa to as much as 1/10. From the eumelanin/pheomelanin ratio, the melanin of brown and dilute brown mice was found to be eumelanic, while the melanin of pink-eyed dilution mice appeared to be a mixed type because of an extremely low content of eumelanin. The levels of bound dopa and 5-S-cysteinyldopa in hair were found to largely reflect the tyrosinase activity.

Differentiation and tumorigenicity of human malignant melanocytes in relation to their culture conditions

The effects of variations in the concentrations of L-cystine (Cys), L-methionine (Met), and L-glutamine (Glu) on the establishment of melanocyte cell lines obtained from a primary tumor and its metastasis in the same patient were studied. The special role of Glu was also studied in 4 lymph node metastases from other patients. Differentiation in vitro was dependent on the culture conditions, as assessed by morphologic and biochemical studies. Karyologic expression, doubling time, cloning efficiency, and tumorigenicity in nude BALB/c mice varied widely among the cell lines. Cys was an indispensable amino acid and Glu was not. Met and Glu were implicated in melanogenesis. From these observations arose the question of the accuracy of comparative results, concerning differentiation and tumorigenicity, that had been collected for cell lines obtained under different culture conditions.

Cysteinyldopa isomers and dopa in lesions and urine of Japanese patients with malignant melanoma

Cysteinyldopas and Dopa in the urine and tissues of Japanese melanoma patients were investigated quantitatively by means of high-performance liquid chromatography. Cysteinyldopa isomers were detected in the urine of eumelanic Japanese patients. The amount (X +/- SD%) of each isomer of cysteinyldopa in the urine was 80.26 +/- 4.66% in 5-S-cysteinyldopa, 9.39 +/- 1.64% in 2-S-cysteinyldopa, 7.07 +/- 3.33% in 2, 5-S, S-dicysteinyldopa, and 3.28 +/- 1.43% in 6-S-cysteinyldopa. The amount of cysteinyldopa in melanoma tissues was 26-314 times more than that of Dopa. The amount (X +/- SD%) of cysteinyldopa in the tissues was 80.34 +/- 1.75% in 5-S-cysteinyldopa, 11.06 +/- 1.91% in 2-S-cysteinyldopa, 6.27 +/- 1.43% in 2, 5-S, S-dicysteinyldopa, and 2.34 +/- 0.61% in 6-S-cysteinyldopa. The fact that the percentages of each isomer of cysteinyldopa in the urine and in the tissues were approximately constant suggests that the cysteinyldopas secreted from melanoma cells were excreted into the urine without being metabolized.

Evidence of dopa in the nerves of sea anemones

An analysis of the presence of catechol-derivatives in the sea anemones Metridium senile and Tealia felina, made with the aid of high-pressure liquid chromatography (HPLC), established the presence of dopa, 5-OH-dopa, and 5-S-cysteinyldopa. In addition, 2-S-cysteinyldopa and 2.5-diSS-cysteinyldopa occurred in Metridium. Two unknown substances were found to be present in the tentacles of Metridium and in the tentacles of some specimens of Tealia. Neither catecholamines nor serotonin could be traced in detectable amounts. No dopa-decarboxylase could be demonstrated by the assay performed in this investigation. 6-OH-dopa, 6-OH-dopamine and reserpine had no effect on the formaldehyde-induced fluorescence of the subepithelial tentacular nerve net of Tealia. It is concluded that the tentacular nerve net of sea anemones contains dopa, but neither catecholamines nor serotonin. The localization of the other compounds is not yet established.

Characterization of structural properties for morphologic differentiation of melanosomes. III. free and protein-bound dopa and 5-S-cysteinyldopa in B16 and Harding-Passey melanomas

This study analyzed the free and protein-bound forms of dopa, 5-S-cysteinyldopa (5-S-CD), and 5-S-glutathionedopa (5-S-GD) in B16 and Harding-Passey (HP) mouse melanomas to investigate the role of these catechols for melanogenesis and melanosome morphogenesis, inasmuch as these tumors produce melanosomes different in color and ultrastructure, i.e., eumelanosome type in B16 and pheomelanosome type in HP. Between B16 and HP mouse melanomas, however, we found (a) no significant difference in the level of free dopa and 5-S-CD in melanosomes and tumors, although the levels of these catechols reflected well the type of melanogenesis in control hair of normal mice, (b) a significant difference in free 5-S-GD level, which might, in part, reflect the observed difference in melanogenesis, and (c) no apparent difference in the level of bound dopa and 5-S-CD in either melanosomes or tumors. Thus, the striking difference in the color of melanosomes between B16 and HP melanomas seems to be related primarily to the content--not the type--of melanin pigments.

5-S-Cysteinyldopa in ganglion stellatum

5-S-Cysteinyldopa, an amino acid formed by nucleophilic addition of cysteine to dopaquinone, has been detected in the ganglion stellatum of the cow in amounts varying between 21 and 35 ng/g ganglionic tissue. Dopa was present in slightly higher quantities. Cysteinyldopa has previously been regarded as a substance unique for the melanocytes, where it forms melanin after oxidation and polymerization. At present only hypothetical explanations of our finding can be offered. The content of 5-S-cysteinyldopa in ganglion stellatum may be the result of dopa oxidation in ganglionic cells. An uptake mechanism for circulating cysteinyldopa may exist. Localization of cysteinyldopa to aberrant melanocytes or to aged SIF-cells in the ganglia should also be borne in mind.

A new approach to the differential diagnosis of human malignant melanomas

In an attempt to improve the diagnosis of melanotic tumors, we have compared the diagnosis obtained by histological examination of 216 skin tumors and their metastases with that obtained by using a conjunction of four techniques: tissue culture, cytoenzymology, in situ electron microscopy and 5-S-cysteinyldopa (5-S-CD) assay. In 46 cases the final diagnosis as determined by one or more of these tests differed from the initial histological diagnosis, but was confirmed by repeat histological examination. We conclude that this method presents a valuable new approach to the differential diagnosis of human malignant melanoma.

Analysis of cysteinyldopas, dopa, dopamine, noradrenaline and adrenaline in serum and urine using high-performance liquid chromatography and electrochemical detection

The catecholic amino acids, dopa, 2-S- and 5-S-cysteinyldopa, and 2,5-S,S-dicysteinyldopa were determined qualitatively in serum from patients with malignant melanoma by reversed-phase high-performance liquid chromatography, using electrochemical detection. In urine the catecholamines dopamine, noradrenaline and adrenaline were also determined qualitatively, as well as the above-mentioned compounds, in a single chromatographic run. The conditions were optimized by changing the pH of the mobile phase and by the addition of methanesulphonic acid. A comparison was made between the performance of four commercial reversed-phase packing materials containing chemically bonded octadecyl groups, using a standard mixture of catecholic amino acids. The influence of ionic strength, pH and amount of methanesulphonic acid on retention was investigated.

Fluorescence histochemical demonstration of dopa thioethers by condensation with gaseous formaldehyde

The usefulness of the formaldehyde (FA) and glyoxylic acid (GA) methods for the fluorescence histochemical demonstration of dopa thioethers has been tested using protein droplet models. Similar fluorescence intensities were recorded from these compounds after either FA or GA treatment. Cysteinyldopa gave a high fluorescence yield similar to that obtained from dopamine and dopa in the FA reaction, whereas gluatitodopa showed a lower, although clearly visible fluorescence. Since the FA method seemed to be the most useful one for demonstration of catechol thioethers, the FA-induced fluorophores of these compounds were further characterized by microspectrofluorometry. The spectral characteristics of the thioether fluorophores (excitation maxima at 420 nm and emission maxima at 480-485 nm) distinguish these substances from dopa and other compounds fluorogenic in the Falck-Hillarp method. Dopa thioethers are proposed to form fluorophores with FA in a manner analogous to that of the primary catecholamines i.e. via low-fluorescent tetrahydroisoquinolines, along two different pathways, to strongly fluorescent 3,4-dihydroisoquinolines and 2-methyl-dihydroisoquinolinium compounds. These dihydroisoquinolines are in a pH-dependent tautomeric equilbrium with their quinoidal forms as reflected by a characteristic spectral shift upon acidification. The results of this study provide the guide-lines for the characterization of fluorogenic compounds in pigment-forming cells.

On the occurrence of cysteinyldopa and dopa in melanocytes and benign nevi cells

Previous studies have demonstrated a specific cytoplasmic fluorescence in human melanocytes, as well as in pigmented nevi and in malignant melanomas, when the formaldehyde histofluorescence method for visualization of certain catechol and indole derivatives was used. In malignant melanoma two fluorogenic substances, dopa and cysteinyldopa, were found previously. In human melanocytes and benign nevi cells the fluorogenic catechols have so far not been characterized, since chemical analyses are difficult to perform on skin, due to the small amounts of catechols present. However, using split thickness skin quantitative determinations are possible by sensitive fluorometric methods. The chemical analyses of cysteinyldopa showed that in human adult skin most or all was located in the superficial layers. The only specific fluorescence in the thin skin was found in dendritic melanocytes. The findings leave little doubt that cysteinyldopa is stored in melanocytes although the possibility of a concomitant occurrence of other thioethers is not excluded. Nevi and giant nevi were also similarly studied and we found considerable amounts of cysteinyldopa in the nevi. It seems as if the cysteinyldopa is stored in the fluorescent nevi cells. There was no consistent difference in the content of the catechol derivatives between intradermal and compound nevi.