1,721,132 research outputs found
Neuromelanin: a key to Parkinson's disease
No full textNeuromelanin and its relation to Parkinson's disease are discusse
Neuromelanin: a key to Parkinson's disease
No full textNeuromelanin and its relation to Parkinson's disease are discusse
A new look at the oxidative chemistry of 5,6-dihydroxyindoles, the key precursors of natural melanin pigments
No full textCaratterizzazione di nuovi derivati tetraidroisochinolinici e fruttosamminici per reazione della dopammina e della L-DOPA con il D-glucosio in condizioni biomimetiche
No full textPictet-Spengler condensation of the antiparkinsonian drug L-DOPA with D-glyceraldehyde. Opposite kinetic effects of Fe3+ and Cu2+ ions and possible implications for the origin of therapeutic side effects.
No full textIn 0.05 M phosphate buffer, pH 7.4. and at 37 degreesC, L-DOPA. a widely used antiparkinsonian drug, reacted smoothly with D-glyceraldehyde to afford diastereoisomeric (1R,1 'S,3S)-3-carboxy-1-( 1 ' .2 ' -dihydroxyethyl)-6,7-dihydroxy- 1,1,3,4-tetrahydroisoquinoline (1) and (1S,1 'S,3S)-3-carboxy-1-( 1 ' ,2 ' -dihydroxyethyl)-6,7-dihydroxy- 1,2,3,4-tetrahydroisoquinoline (2) in an approx. 3:2 ratio. The prevalent formation of 1 over 2 reflects stereoselective cyclisation of a transient Schiff base in accord with the Felkin-Anh model. Fe3+ ions, present at relatively high levels in parkinsonian brains, markedly accelerated formation of 1 and 2. whereas Cu2+ decreased the reaction rate, due apparently to different sites of chelate formation between L-DOPA and the metal ions. Both metal ions markedly decreased the stereoselectivity of the reaction. Product 1 exhibited chelating properties toward metal ions comparable or stronger than those of L-DOPA. These results throw new light on the effects of transition metal ions on the Pictet-Spengler reaction and suggest a possible role of tetrahydroisoquinoline products from L-DOPA and carbohydrate metabolites in the severe side effects of the drug
A re-examination of the zinc-catalysed rearrangement of dopachrome using immobilised tyrosinase
No full textThe rearrangement of the melanogenic intermediate melanochrome in the presence of metal ions was examine
A profile of the oxidation chemistry of 5-hydroxyindole under biomimetic conditions
No full textIn aqueous buffer, at physiological pHs, 5-hydroxyindole (3) is rapidly oxidised by the H2O2/horseradish peroxidase system to give a complex mixture of oligomeric products, five of which could be isolated after acetylation, and identified as the diacetoxybiindolyls 4 and 5, and the trimers 6, 7 and 8. A similar pattern of products was obtained from the reaction of 3 with other oxidising agents, e.g. potassium ferricyanide, ammonium persulphate and sodium periodate. The Observed reactivity suggests that oxidation of 3 proceeds probably through the intermediacy of the labile quinone Inline 9. This could be trapped In the form of the adduct 12 when 3 was oxidised with o-chloranil in dry ether. © 1988
PRADER-WILLI SYNDROME: ORAL FINDINGS
Full text linkAim: Prader-Willi syndrome is a rare multisystemic genetic disorder
caused by lack of expression of certain paternal genes
located on chromosome 15.
The syndrome, associated to hypothalamic and pituitary disfunction,
is characterized by severe neonatal hypotonia and
feeding problems. Neonatal hypotonia is followed, during
childhood by hyperphagia and obesity. In addition, hypothalamic
alterations can cause intellectual disability, behavioral
problems, a high pain threshold, respiratory sleep disorders.
The aim of this work is to evaluate the main dental aspects and
the therapeutic implications.
Methods: an analysis of the literature was performed using
databases.
Results: common clinical findings: gingivitis and periodontitis,
dental and skeletal malocclusions, enamel hypoplasia, tooth wear
and dental erosion, bruxism, xerostomia, candidiasis and angular
cheilitis, high risk of caries and increased DMFT score.The typical
poor oral hygiene in PWS patients is related to qualitative-quantitative
changes in saliva and incoordination in tooth brushing.
Conclusion: it is necessary to motivate family and patient to
maintain oral hygiene. Due to the various systemic and dental
problems, a six-monthly follow-up is required since early childhood.
Dental treatment purposes require a multidisciplinary
approach which includes periodontal and conservative cares.
In prosthetics, we suggest the use of removable dentures because
of the difficulty in maintaining oral hygiene
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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