Herbivores can ingest and store plant-synthesized toxic compounds in their bodies, and sequester those compounds for their own benefits. The broad bean, Vicia faba L., contains a high quantity of L-DOPA (L-3,4-dihydroxyphenylalanine), which is toxic to many insects. However, the pea aphid, Acyrthosiphon pisum, can feed on V. faba normally, whereas many other aphid species could not. In this stu...

In this study, the protective effects of EGCG on L-3,4-dihydroxyphenylalanine (L-DOPA)-induced oxidative cell death in catecholaminergic PC12 cells, the in vitro model of Parkinson's disease, were investigated. Treatment with L-DOPA at concentrations higher than 150 µM caused cytotoxicity in PC12 cells, as determined using the 3-(4,5-dimetylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) as...

Mammalian tyrosinase as currently defined has two catalytic functions: 1) the oxidation of tyrosine to L-3,4-dihydroxyphenylalanine (dopa) and 2) the oxidation of dopa to dopa quinone (1-9). Although an imposing body of evidence has been advanced in support of this interpretation, Okun and associates have recently challenged the prevailing concept of the action of tyrosinase ( 10, 11 ). They ha...

The intrarenal autocrine-paracrine dopamine (DA) system is critical for Na(+) homeostasis. l-Dihydroxyphenylalanine (l-DOPA) uptake from the glomerular filtrate and plasma provides the substrate for DA generation by the renal proximal tubule. The transporter(s) responsible for proximal tubule l-DOPA uptake has not been characterized. Renal cortical poly-A(+) RNA injected into Xenopus laevis ooc...

L-dopa is a precursor of dopamine used as the most effective symptomatic drug treatment for Parkinson’s disease. Most isolated either synthesized chemically or from natural sources, but only some plants belonging to Fabaceae family contain significant amounts L-dopa. Due its low stability, unambiguous determination in plant matrices requires appropriate technologies. Several analytical methods ...

BACKGROUND The absence or deficiency of melanin as in albinos, has detrimental effects on retinal development that include aberrant axonal projections from eye to brain and impaired vision. In pigmented retinal pigment epithelium (RPE), dihydroxyphenalanine (L-Dopa), an intermediate in the synthetic path for melanin, has been hypothesized to regulate the tempo of neurogenesis. The time course o...

We have examined the ability of KW-6002, an adenosine A2a antagonist, to modulate the dyskinetic effects of L-DOPA in 6-hydroxydopamine-lesioned rats. In animals rendered dyskinetic by a previous course of L-DOPA treatment, KW-6002 did not elicit any abnormal involuntary movements on its own, but failed to reduce the severity of dyskinesia when coadministered with L-DOPA. A second experiment wa...

BACKGROUND AND PURPOSE L-DOPA is still the most efficacious pharmacological treatment for Parkinson's disease. However, in the majority of patients receiving long-term therapy with L-DOPA, its efficacy is compromised by motor complications, notably L-DOPA-induced dyskinesia. Evidence suggests that the serotonergic system is involved in the therapeutic and the side effects of L-DOPA. Here, we in...

L-dopa remains the mainstay treatment for Parkinson's disease (PD), although in later stages, treatment is complicated by L-dopa-induced dyskinesias (LID). Current evidence links LID to excessive striatal L-dopa-derived dopamine (DA) release, while the possibility of a direct involvement of L-dopa itself in LID has been largely ignored. Here we show that L-dopa can alter basal ganglia activity ...

Monoaminergic neurons use dopa decarboxylase (DDC; aromatic-L-amino-acid carboxy-lyase, EC 4.1.1.28) to form dopamine from L-3,4-dihydroxyphenylalanine (L-dopa). We measured regional dopa decarboxylase activity in brains of six healthy volunteers with 6-[18F]fluoro-L-dopa and positron emission tomography. We calculated the enzyme activity, relative to its Km, with a kinetic model that yielded t...