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PubMed1990

In vivo autoxidation of dopamine in guinea pig striatum increases with age.

Catechols are known to react readily with molecular oxygen to form the corresponding quinones together with reduced oxygen species. These products have been shown to be toxic in in vivo and in vitro systems. 5-S-Cysteinyl adducts of catechols are believed to be formed through the spontaneous reaction between quinones and thiol-containing compounds, like cysteine and glutathione (GSH). Thus, the brain levels of these adducts probably indicate the autoxidation rate of catechols in vivo. In the present study, the striatal concentrations of 5-S-cysteinyldopamine (5-S-cysteinyl-DA), 5-S-cysteinyl-3,4-dihydroxyphenylalanine (5-S-cysteinyl-DOPA), and 5-S-cysteinyl-3,4-dihydroxyphenylacetic acid (5-S-cysteinyl-DOPAC) were determined in 2-week-, 2-month- and 3-year-old guinea pigs. In addition, brain levels of DA, the DA metabolite DOPAC, and GSH were assessed. The concentration of 5-S-cysteinyl-DA increased markedly with age. The 3-year-old guinea pigs had the highest level, i.e., 248% of the concentration in the 2-week-old animals and 219% of the concentration in the 2-month-old animals. Furthermore, the striatal 5-S-cysteinyl-DOPA level in the 3-year-old group was 68% higher than in the 2-week-old group and 46% higher than in the 2-month-old group. No age difference in the striatal concentration of DA was found. In contrast, the concentration of DOPAC increased with age: The DOPAC level in the 3-year-old animals was 153% of the level in the 2-week-old animals and 116% of the level in the 2-month-old animals.(ABSTRACT TRUNCATED AT 250 WORDS)

3,4-Dihydroxyphenylacetic Acid↗
PubMed1987

Ultraweak photon emission in model reactions of the in vitro formation of eumelanins and pheomelanins.

Ultraweak luminescence in the spectral region 300-660 nm is generated in the enzymatic (tyrosinase EC.1.14.18.1) and autooxidative polymerization of L-DOPA, 5-S-cysteinyl-DOPA, and L-DOPA + cysteine to eumelanins and pheomelanins, respectively. Using sensitive calibrated single photon counting equipment, the photon emission intensity I and quantum yield phi have been measured: I = 10-100 h nu/s cm3, phi less than or equal to 10(-13) for enzymatic reactions, and I = 500-3000 h nu/s cm3, phi greater than or equal to 5 x 10(-12) for autooxidative ones. 5-S-cysteinyl-DOPA and cysteine exhibit diminished I and phi-values relative to DOPA. Tests with chemiluminogenic probes-luminol and lucigenin, SOD, catalase, peroxidase, H2O2, and spectrophotometric measurements indicate that photon emission is associated with degradative oxidations of melanin subunits by means of active oxygen species as H2O2 and O2.

Catechol Oxidase↗
PubMed1992

Regulatory factors of pheo- and eumelanogenesis in melanogenic compartments.

Melanogenesis, i.e., synthesis of melanin and melanosomes, is a "cascade" of event which is channelled by internal and external regulatory factors. The recognition and selection of this information and subsequent differentiation of melanogenesis (melanin type and melanosomal development) would be regulated significantly by melanosomal membrane. The melanogenesis type could be switched relatively easily by UV light, hormone, and availability of tyrosinase substrate. The role of sulphydryl compounds as a regulatory factor in melanogenesis type (in particular for pheomelanogenesis) may not be tied to its absolute presence or absence, but rather, to the effective concentration within the melanocyte at a given time. It is, therefore, probable that the morphogenesis of melanosomes may not follow immediately in response to melanogenesis-type changes, hence the melanocyte revealing more often mosaic forms of melanosomes in nature after exposure to non-genetic factors. The switch of melanogenesis would be significantly controlled by structural and functional availability of vesiculoglobular bodies which are encoded or associated with HMSA-5 (69 kDa) glycoprotein. This HMSA-5 protein shares a significant homology with gp75 "b-locus" protein. However, because of our hypothesis that vesiculoglobular bodies carry post- (and pre-) tyrosinase regulatory factors involving in both pheo- and eumelanogenesis, the term "b-protein" which focuses only on eumelanogenesis may not be applied to HMSA-5.

Animals↗
PubMed1996

Levodopa and deprenyl treatment effects on peripheral indices of oxidant stress in Parkinson's disease.

The oxidant stress theory of Parkinson's disease (PD) hypothesizes that levodopa treatment may be potentially harmful and this is supported by studies demonstrating levodopa toxicity to cultured dopaminergic neurons. These in vitro experiments, however, lack the physiologic protective mechanisms present in vivo. Oxyradical damage to cell membranes liberates malondialdehyde, which we measured in the serum of 27 PD patients just before and after levodopa (with carbidopa) administration. We also measured plasma products of the two routes by which levodopa potentially generated oxyradicals: (1) 5-S-cysteinyl-dopa (derived from levodopa autoxidation), and (2) 3,4-dihydroxyphenylacetic acid (DOPAC), produced by monoamine oxidase (MAO) metabolism of dopamine. Following levodopa/carbidopa administration, both of these plasma products were markedly increased; however, the mean serum malondialdehyde concentration was unchanged and remained similar to the normal control group (N=15) value. Chronic treatment with the MAO-B inhibitor, deprenyl (N=16), was not associated with any differences in serum malondialdehyde or plasma 5-S-cysteinyl-dopa concentrations compared with those not treated with deprenyl (N=11). The post-levodopa rise of plasma DOPAC was only slightly attenuated with deprenyl therapy, consistent with a predominant MAO-A effect in the circulation and peripheral organs. Thus, in contrast to in vitro studies, we did not detect evidence of oxidative damage in the circulation following levodopa administration, despite marked increase in the products of dopamine oxidative metabolism.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1987

Enhancement of pheomelanogenesis by L-dopa in the mouse melanocyte cell line, TM10, in vitro.

Cells of TM10, an established cell line, are melanocytes that contain equal amounts of eumelanin (black pigment) and pheomelanin (yellow pigment). The content of pheomelanin drastically increased when the cells were cultured in growth medium containing 0.2mM-L-dopa (L-dihydroxyphenylalanine), which is the common precursor for both eumelanogenesis and pheomelanogenesis. After this treatment, the amount of pheomelanin was 3.7-fold greater than that of control in TM10, whereas the amount of eumelanin changed very little. In contrast, 5-S-cysteinyl-dopa, which is the specific precursor for pheomelanogenesis downstream of L-dopa, did not cause preferential increase in pheomelanogenesis. Ultrastructural observations also confirmed these results; in 0.2mM-L-dopa, an increase in the number of pheomelanosomes was observed in the cytoplasm of TM10 cells. Our results also suggest that the L-dopa treatment results in a decrease in tyrosinase activity per melanosome.

Animals↗
PubMed1990

[Tyrosine and methionine metabolism in various states of melaninogenesis].

Excretion with urine of tyrosine and methionine metabolites as well as the activities of enzymes involved in their metabolism are correlated with the state and type of melanin synthesized in the skin. The response of tyrosine aminotransferase to melaninogenesis induction was more pronounced in animals with predominant pheomelaninogenesis, especially after tyrosine load, while that to dopachrome oxidoreductase--in animals with predominant eumelaninogenesis and after methionine load. Glutathione reductase and cystathionine-beta-synthase responded more vigorously to methionine injections, which was especially well pronounced in animals with prominent pheomelaninogenesis and in albino animals. The metabolic "block" in melanine synthesis in albino animals seems to be observed after the 5-S-cysteinyl-DOPA synthesis, whereas the initial steps of melaninogenesis in these animals are identical to pheomelanine synthesis reactions.

Animals↗
PubMed1990

[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.

Adolescent↗
PubMed1978

[Pheomelanins].

Explore the source record for details and available documents.

Animals↗
PubMed1993

Exploitation of pigment biosynthesis pathway as a selective chemotherapeutic approach for malignant melanoma.

Human malignant melanoma represents a difficult therapeutic challenge to both medical scientists and practicing physicians. However, the biologic uniqueness of the tumor may provide opportunities for exploitation in therapeutics. This study proposed to undertake a systemic approach to the chemotherapy of malignant melanoma based upon the uniqueness of pigment-cell metabolic pathway pertaining to conversion of tyrosine and dopa with subsequent formation of melanin by tyrosinase and its related enzymes. The sulphur homologue of tyrosine, cysteinylphenol (CP), its amine derivative, cysteaminylphenol (CAP), and their N-acetyl and alpha-methyl derivatives have been synthesized and tested in in vivo and in vitro melanocytotoxicity and antimelanoma effects. These phenolic thioethers (PTEs) and phenolic thioether amine (amides) (PTEAs), which are substrates of tyrosinase, showed significant cytotoxicity that is selective to melanocytes and melanoma cells. Most previous attempts to impair the melanin pathway as a therapeutic strategy have been of limited success because they have been directed to catecholic compounds that are unstable and insufficient in lethality at physiologically tolerable doses. By contrast, our approach relies on phenolic compounds, PTEs and PTEAs, which are more stable than catechols and become toxic only after oxidation by tyrosinase. We found PTEA as the most promising agent for the future development of chemotherapeutic agents. The possible biologic, chemical, and pharmacologic reactions of these synthetic compounds within the melanoma cells are studied and discussed.

Benzoquinones↗
PubMed1996

Two cases of metastatic malignant melanoma of the lower limb treated with hyperthermic isolated limb perfusion and concomitant infusion of either carboplatin or beta-interferon.

Two cases of metastatic malignant melanoma of the lower limb who were treated successfully with hyperthermic isolated limb perfusion are reported. One patient was infused with cisdiammine (1.1-cyclobutanedicarboxylate) platinum (II) (carboplatin, Paraplatin, Bristol-Myers Squibb Company, New Jersey, USA), and the other was infused with human natural beta-interferon (Feron, Toray, Tokyo, Japan), via the external iliac artery. The first case showed a remarkable suppression of the growth of multiple metastatic melanoma nodules associated with numerous melanophage infiltrations, as shown histopathologically after the operation. The patient's serum level of 5-S-cysteinyl dopa decreased for the two months following the treatment. In the second case, new formation of metastatic melanoma nodules was completely suppressed for up to 12 months following the operation. Analysis of immunological parameters showed that the number of peripheral CD8+ lymphocytes gradually and constantly increased after the operation, while that of CD4+ lymphocytes transiently increased and then returned to the pre-operative level. Natural killer activity transiently decreased to a slight degree 4 days after the operation and then returned to the pre-operative level 21 days after the operation. Side effects, such as nausea, vomiting and leg discomfort, were seen in the patient (Case 1) treated with carboplatin, but were completely reversible. These results suggest that hyperthermic isolated limb perfusion with concomitant infusion of carboplatin or beta-interferon is effective in suppressing the growth of metastatic malignant melanomas of the lower limb.

Aged↗
PubMed1976

Detection of occult metastatic melanoma by urine chromatography.

By using ion-exchange column chromatography with effluent monitoring using the stable, free radical alpha,alpha-diphenyl-beta-picryhydrazyl as a colorimetric reagent, we have demonstrated the occurrence of elevated levels of five peaks in the urine of patients with metastatic disease. The tentative assignment of two of the peaks as 3,4-dihydroxyphenylalanine and as 3-methoxy-4-hydroxyphenylalanine has been made. Three remain unknown. The correlation of these peaks with the clinical status of melanoma patients shows that, while the individual excretion pattern of these compounds may be variable, the sustained occurrence of one or more of them in a patient's urine is evidence of recurrent or continuing disease. The excretion levels appear to be proportional to the tumor burden. The results with a group of 39 melanoma patientshaving Stage II or Stage III disease indicate that this chromatography technique provides earlier evidenc eof liver metastases than doses the liver scan, may detect occult metastases generally, and has detected tumor in clinically enlarged lymph nodes. This method, in its present form, does not detect small pulmonary lesions earlier than chest X-ray or tomography do or brain metastases earlier than do brain scan or computerized axial tomography. The technique is clinically useful for the diagnosis of melanoma patients and in their follow-up while under treatment.

Chromatography, Ion Exchange↗