In normal individuals, the main route for tyrosine degradation is the hepatic pathway tyrosine→4-hydroxyphenylpyruvic acid→homogentisic acid→CO(2). Quantitatively minor pathways, in large part extrahepatic, are: tyrosine→tyramine→octopamine and tyrosine→dopa→catecholamines.In cirrhosis, the main hepatic pathway is blocked to varying degrees at the first three stages. This appears to be due to l...

The role of L-DOPA in spinal nociceptive reflex activity has been re-evaluated. In high spinal cats, with supraspinal loops being excluded, the onset of reflex facilitation induced by noxious radiant heat is delayed after injection of L-DOPA by 4 to 10 s, i.e. the early component of nociceptive reflex facilitation is blocked, while the late component persisted. Further investigations have shown...

Melanin synthesis in mammals is catalysed by at least three enzymic proteins, tyrosinase (monophenol dihydroxyphenylalanine:oxygen oxidoreductase, EC 1.14.18.1) and tyrosinase-related proteins (tyrps) 1 and 2, whose genes map to the albino, brown and slaty loci in mice, respectively. Tyrosinase catalyses the rate-limiting generation of L-dopaquinone from L-tyrosine and is also able to oxidize L...

In Parkinson's disease, impaired motor preparation has been related to an increased latency in the appearance of movement-related desynchronization (MRD) throughout the contralateral primary sensorimotor (PSM) cortex. Internal globus pallidus (GPi) stimulation improved movement desynchronization over the PSM cortex during movement execution but failed to improve impaired motor preparation. PET ...

We developed a new detection method for L-Dopa decarboxylase (DDC) activity using gold nanoparticles (AuNPs). When L-3,4-dihydroxyphenylalanine (L-Dopa) is decarboxylated to dopamine (DA) by DDC, DA induces the aggregation of AuNPs, and the color of the AuNPs changes from red to blue.

The SLC45A2 gene encodes a Membrane-Associated Transporter Protein (MATP). Mutations of this gene cause oculocutaneous albinism type 4 (OCA4). However, the molecular mechanism of its action in melanogenesis has not been elucidated. Here, we discuss the role of MATP in melanin production. The SLC45A2 gene is highly enriched in human melanocytes and melanoma cell lines, and its protein, MATP, is ...

The most effective treatment for Parkinson's disease (PD), l-DOPA, induces dyskinesia after prolonged use. We have previously shown that in 6-hydroxydopamine (6-OHDA) lesioned rats rendered dyskinetic by prolonged l-DOPA administration, lesion of the subthalamic nucleus (STN) reduces not only dyskinesias but also buspirone antidyskinetic effect. This study examined the effect of buspirone on ST...

Seasonal changes in reproduction and other metabolic conditions may result from interaction of circadian neural oscillations and hormonal secretion that change seasonally. To test this hypothesis, the present study was designed to study the effect of melatonin and circadian neurotransmitter activity on reproductive and hormonal conditions in a subtropical finch, spotted munia (Lonchura punctula...

The HPTLC analysis, antioxidant, and antigout activity of Asparagus racemosus, Withania somnifera, Vitex negundo, Plumbago zeylanica, Butea monosperma and Tephrosia purpurea extracts were investigated. The chemical fingerprinting were carried out by high performance thin layer chromatography (HPTLC), antioxidant activity by ABTS, DPPH, FRAP radical scavenging assays, and antiogout activity by c...

We have initiated a study of catecholamine-containing neurons in Drosophila melanogaster because of the potential, with this organism, to perturb catecholamine metabolism using genetic tools. The major objectives of this study were (1) to define the pattern of catecholamine-containing neurons and (2) to determine the effect of the absence of dopa decarboxylase (DDC) enzyme activity on the catec...