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At least 145 records · Page 8Linked to original sources
PubMed1978

Dopaminergic control of adenohypophyseal growth after oestrogens: negative results with L-DOPA, RO-4-4602, alpha-methyl-DOPA, apomorphine, haloperidol, pyridoxine and cyproheptadine.

Chronic oestrogen treatment augments adenohypophyseal weight and the thyroxine-binding capacity of adenohypophyseal proteins in rats. Since these reactions are both inhibited by ergocornine and ergoline derivatives (as well as by the thyroid hormones, testosterone, anti-oestrogens and antiandrogens), and are potentiation by perphenazine and the dopaminergic neurone blocker Pimozide, the peroral effectiveness of various other substances presumed to act in the region of the dopaminergic or serotoninergic neurones of the hypothalamus was tested. L-DOPA (10 mg/rat/day) did not modify the adenohypophyseal reaction, either alone or combined with the DOPA-decarboxylate inhibitor Ro-4-4602 (1 mg/rat/day). alpha-Methyl-DOPA (10 mg/rat/day), apomorphine (3 mg/rat/day), haloperidol (0.2 mg/rat/day), pyridoxine (20 mg/rat/day) and cyproheptadine (1 mg/rat/day) were likewise ineffective.

Animals↗
PubMed1995

Apomorphine SC treatment in parkinsonian patients with long-term L-dopa syndrome during L-dopa drug holiday.

The Long-Term Dopa Syndrome (LTDS) is one of the main problems in the management of advanced parkinsonian patients. A transient L-Dopa withdrawal (Drug Holiday, DH) can be useful to improve the drug response after DH, even if this approach presents risks due to patient akinesia. We tried to verify if Apomorphine sc administration during DH (DH with Apomorphine, DHA) can: a) reduce the risks connected with DH: b) maintain the benefits of DH: c) standardize the duration of DH. Twenty-five parkinsonian patients with LTDS were treated with Apomorphine sc during DH (14 days). No patient had any severe side effects. The follow-up at 180 days, conducted using the Unified Parkinson's Disease Rating Scale, demonstrated a significant improvement in the clinical conditions of about 70% of the patients, allowing a 27.1% reduction in daily L-dopa dosage. DHA can represent a valid therapeutical approach for parkinsonian patients with LTDS.

Adult↗
PubMed1983

Use of radiolabeled monofluoromethyl-Dopa to define the subunit structure of human L-Dopa decarboxylase.

Human L-Dopa decarboxylase (L-aromatic amino acid decarboxylase, DDC) has been purified from pheochromocytoma tissue, a benign tumor of the catecholamine-synthesizing cells of the adrenal medulla. The binding characteristics of a new radiolabeled enzyme-activated suicide inhibitor of DDC ( [3H]monofluoromethyl-Dopa, [3H]MFMD) have been established, and the covalent linkage of the inhibitor to the enzyme has been used to identify that human DDC exists as a dimer of a 50-kDa subunit. An antibody to human DDC identically precipitates the enzyme activity from different human, rat, and mouse tissues. Our data demonstrate the value of [3H]MFMD for probing the structure of DDC and facilitating the purification of this enzyme, and further emphasize the high degree of conservation of the DDC molecule over a wide variety of species.

Animals↗
PubMed1979

Reactions of DOPA (3,4-dihydroxyphenylalanine) decarboxylase with DOPA.

The study of DOPA (3,4-dihydroxyphenylalanine) decarboxylase by steady-state methods is difficult because multiple reactions occur. The reaction with DOPA was studied at enzyme concentrations between 20 and 50 micrometer by direct observation of the bound coenzyme by using stopped-flow and conventional spectrophotometry. Four processes were observed on different time scales and three of these were attributed to stages in the decarboxylation. The fourth was attributed to an accompanying transamination that renders the enzyme inactive. It was clear that much, if not all, of the 330 nm-absorbing coenzyme present in the free enzyme plays an active part in the decarboxylation, since it is converted into 420 nm-absorbing material in the first observable step. An intermediate absorbing maximally at 390 nm is formed in a slower step. Rate and equilibrium constants have been determined and the ratio of decarboxylation to transamination was estimated to be 1200:1.

Amination↗
PubMed2003

Acute double-blind, placebo-controlled sleep laboratory and clinical follow-up studies with a combination treatment of rr-L-dopa and sr-L-dopa in restless legs syndrome.

In a double-blind, placebo-controlled randomized crossover trial, the acute efficacy of a combination treatment of 100 mg regular-release (rr) and 100 mg sustained-release (sr) L-dopa/benserazide in RLS was investigated by means of sleep laboratory methods, with a subsequent open clinical follow-up for 4 weeks. 21 RLS patients classified according to ICSD and IRLSSG criteria were included; 18 completed the study. Objective sleep quality was determined by polysomnography (PSG) in 3 subsequent nights (adaptation/screening, placebo and drug night), subjective sleep and awakening quality was evaluated by rating scales, objective awakening quality by psychometric tests. Clinical follow-up consisted of daily ratings of subjective sleep and awakening quality (SSA) and VAS for RLS symptomatology ratings, completion of the RLS (IRLSSG) Scale weekly and the Zung Depression (SDS) and Anxiety (SAS) Scale, Quality of Life Index, Pittsburgh Sleep Quality Index and Epworth Sleepiness Scale before and after therapy. Acute L-dopa/benserazide significantly (p < 0.001) and markedly (75%) decreased the target variable PLM/h of sleep as well as all other RLS/PLM variables, but failed to improve objective sleep efficiency and subjective sleep quality in comparison to placebo. After 4 weeks of therapy, however, subjective sleep and awakening quality also improved significantly. While RLS/PLM measures showed an immediate significant and marked response to the combination therapy subjective sleep quality only improved after chronic treatment.

Adult↗
PubMed2004

The NR2B-selective NMDA receptor antagonist CP-101,606 exacerbates L-DOPA-induced dyskinesia and provides mild potentiation of anti-parkinsonian effects of L-DOPA in the MPTP-lesioned marmoset model of Parkinson's disease.

In Parkinson's disease (PD), degeneration of the dopaminergic nigrostriatal pathway leads to enhanced transmission at NMDA receptors containing NR2B subunits. Previous studies have shown that some, but not all, NR2B-containing NMDA receptor antagonists alleviate parkinsonian symptoms in animal models of PD. Furthermore, enhanced NMDA receptor-mediated transmission underlies the generation of L-DOPA-induced dyskinesia (LID). The subunit content of NMDA receptors responsible for LID is not clear. Here, we assess the actions of the NMDA antagonist CP-101,606 in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned marmoset model of Parkinson's disease. CP-101,606 is selective for NMDA receptors containing NR2B subunits, with higher affinity for NR1/NR2B complexes compared to ternary NR1/NR2A/NR2B complexes. CP-101,606 had no significant effect on parkinsonian symptoms when administered as monotherapy over a range of doses (0.1-10 mg/kg). CP-101,606 provided a modest potentiation of the anti-parkinsonian actions of L-DOPA (8 mg/kg), although, at doses of 1 and 3 mg/kg, CP-101,606 exacerbated LID. Results of this study provide further evidence of differences in the anti-parkinsonian activity and effects on LID of the NR2B subunit selective NMDA receptor antagonists. These distinctions may reflect disparities in action on NR1/NR2B as opposed to NR1/NR2A/NR2B receptors.

Animals↗
PubMed2004

Evaluation of rat striatal L-dopa and DA concentration after intraperitoneal administration of L-dopa prodrugs in liposomal formulations.

Parkinson's disease is a neurodegenerative disease and its symptoms are relieved by administration of L-dopa (LD), which is converted by neuronal aromatic L-aminoacid decarboxylase (AADC), restoring dopamine (DA) levels in surviving neurons. In order to minimize unfavourable side effects, we studied new dimeric LD derivatives, as potential prodrugs for Parkinson's therapeutic treatment. To improve the bioavailability of the synthesized prodrugs, they were encapsulated in unilamellar liposomes of dimiristoylphosphatidylcholine (DMPC) and cholesterol (CHOL). In vivo microdialysis was used to monitor the striatal LD and DA concentrations after i.p. administration of new delivery systems. Bioavailability evaluation was performed by means of the HPLC-EC method. The striatal levels of LD and DA were remarkably elevated after i.p. administration of liposomal formulation of prodrug (+)-1b ([(O,O-diacetyl)-L-dopa-methylester]-succinyldiamide). This formulation showed about 2.5-fold increase in the basal levels of DA in dialysate rat striatum, suggesting that liposomal formulation of (+)-1b significantly increases LD and DA concentrations with respect to equimolar administration of LD itself or free prodrug (+)-1b.

Amides↗
PubMed1989

Characterization of third chromosome dominant alpha-methyl dopa resistant mutants (Tcr) and their interactions with l(2)amd alpha-methyl dopa hypersensitive alleles in Drosophila melanogaster.

In Drosophila melanogaster two alleles at the Third chromosome resistance locus (Tcr; 3-39-6) were isolated in a screen of EMS mutagenized third chromosomes for dominant resistance to dietary alpha-methyl dopa, alpha-MD, a structural analogue of DOPA. Both alleles of Tcr are recessive lethals exhibiting partial complementation. Almost half (48.3%) of the Tcr40/Tcr45 heterozygotes die as embryos but some survive past adult eclosion. Both the embryonic lethal phenotype and the adult phenotype suggest that Tcr is involved in cuticle synthesis. Tcr mutants suppress the lethality of partially complementing alleles at the alpha-MD hypersensitive locus, l(2)amd. The viability of Tcr40/Tcr45, however, is not increased by the presence of a l(2)amd allele. The possibility that the Tcr and l(2)amd mutations reveal a catecholamine metabolic pathway involved in cuticle structure is discussed.

Alleles↗
PubMed1977

MAO activity in rat brain stem and cerebral cortex following acute and chronic treatment with L-dopa and ethanol + L-dopa.

This work reports the effects of acute and chronic administration of L-dopa and ethanol + L-dopa on MAO activity in rat brain stem and cerebral cortex using noradrenaline (NA), dopamine (DA), serotonin (5-HT) and tryptamine (Try) as substrates. The results obtained clearly demonstrate that acute and chronic treatment affects MAO activities in the two brain areas examined in opposite ways. Moreover, the two treatments show different effects both according to the substrate used, and, especially in the case of NA and Try, according to the brain area examined.

Animals↗
PubMed2000

Dopa-responsive dystonia: mutation analysis of GCH1 and analysis of therapeutic doses of L-dopa. German Dystonia Study Group.

Analysis of the gene GCH1 in 58 patients with dystonia and a positive response to L-dopa revealed mutations in 30 individuals from 22 families. Thirteen of the mutations observed were familial, three occurred de novo, and inheritance could not be determined in six cases. There was no mutation in the promoter region of GCH1 in any patient. The doses of L-dopa given to members of the two groups were not significantly different.

Adult↗
PubMedDate not supplied

[Preliminary assessment of the effectiveness of L-dopa with prolonged action (Medidopa retard) as compared to conventional L-dopa preparation].

The therapeutic effectiveness of a L-DOPA preparation of sustained action was established in 9 patients with parkinsonism on the basis of a neurological parkinsonism scale and Northwestern University Disability Scale. The investigations were carried out by the method of cross test with conventional L-DOPA preparation (Larodopa). In these investigations no higher effectiveness of the retard form was shown. Side effects during administration of the retard form were more frequent and more intense than during administration of the conventional drug.

Aged↗
PubMed1983

Age-dependent depressor effect of L-dopa in dogs with inhibition of extracerebral dopa decarboxylase.

The results of this study demonstrate that a carbidopa-L-dopa combination has a greater depressor effect in puppies than in adult dogs. These effects are believed to be due to the action of a metabolite of L-dopa within the CNS. These data should alert clinicians to the possibility that CNS cardiovascular control centers, which utilize catecholamines as neuromediators, may be more responsive to pharmacological stimulation in the young than in the adult.

Aging↗
PubMed1979

Plasmatic renin activity in patients treated with L-dopa and inhibitor of dopa decarboxylase (IDC).

Plasmatic renin activity (PRA) was studied in patients receiving L-dopa, together with a decarboxylase inhibitor, at rest times and after periods of physical exertion. Although we can superimpose the results from unrelated Parkinson's disease patients on those of the control group, the results are inversed in stabilized patients (lowered PRA) and dyskinetic patients (increased PRA). There is a definite correlation between the increase in PRA and intensity of the dyskinesia. Dosage is the only other factor differentiating the two groups of Parkinsonians treated. The figures relative to arterial pressure are studied in the various groups.

Adult↗
PubMed1986

High yield synthesis of 6-[18F]fluoro-L-dopa by regioselective fluorination of protected L-dopa with [18F]acetylhypofluorite.

Regioselective fluorination of a completely protected phosgene derivative of 3,4-dihydroxy-phenyl-L-alanine (5-(benzyl-3',4'-carbonate)-oxazolidine-2,5-dione) with gaseous 18F-labeled acetylhypofluorite and [18F]F2 in acetonitrile is described. Fluorination with [18F]acetylhypofluorite yields 6-[18F]fluoro-L-dopa with 95% radiochemical purity; fluorination of the same substrate with [18F]F2 yields a mixture of all three structural isomers in a ratio of 70:16:14 for 6-, 5-, and 2-fluoro compounds. Radiochemical yield, relative to [18F] acetylhypofluorite, measured at the end of the synthesis, is (21 +/- 4)% (N = 8). The synthesis requires approximately 40 min (50 min if HPLC was done) and yields the final radiopharmaceutical in a two-step procedure. The specific activity of the final product was approximately 763 mCi/mmol at the end of a 40-min synthesis when 30-min irradiation was used.

Acetates↗