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The application of a knowledge based system to micro-electrode guided neurosurgeryHarley, Linda Rosemary 04 February 2004 (has links)
Parkinson's Disease can be treated by a micro-electrode guided neurosurgery called a Pallidotomy or Deep Brain Stimulus. A new software program, called Onetrack, is being developed and incorporates a three dimensional virtual model of the brain, a advanced digital signal processor and a knowledge based system (KBS). This thesis discusses the design and development of this KBS. The purpose of the KBS is to assist the surgical team in identifying the different anatomical structures and neuronal cell types of the brain. Therefore, improving the efficiency of the procedure.
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Lysosomal network proteins as biomarkers and therapeutic targets in neurodegenerative diseaseBoman, Andrea January 2015 (has links)
The pre-symptomatic stage of neurodegenerative diseases such as Alzheimer’s disease (AD) and Parkinson’s disease (PD) occurs several decades before the clinical onset. Changes in the lysosomal network, i.e. the autophagosomal, endosomal and lysosomal vesicular system, are among the first alterations observed. There are currently no treatments to slow or cure neurodegenerative diseases, and there is a great need for discovery of treatment targets in cellular pathways where pathology pre-dates the neuronal death. It is also crucial to be able to diagnose neurodegenerative diseases earlier, both to enable early intervention treatment and aid in selecting clinical trial populations before the patient has widespread pathology. This thesis aims at investigating the potential of lysosomal network proteins as biomarkers and therapeutic targets in neurodegenerative disease. A targeted search for lysosomal network proteins was performed in cerebrospinal fluid (CSF) from AD patients, and seven proteins: early endosomal antigen 1 (EEA1), lysosomal-associated membrane proteins 1 and 2 (LAMP-1, LAMP-2), lysozyme, microtubule-associated protein 1 light chain 3 (LC3), Rab3 and Rab7, were elevated. The levels of EEA1, LAMP-1, LAMP-2, LC3, lysozyme and Rab3 were also measured in CSF from parkinsonian syndrome patients: PD, clinically diagnosed 4-repeat tauopathy, pathologically confirmed corticobasal degeneration (CBD) and pathologically confirmed progressive supranuclear palsy (PSP) patients. LAMP-1 and LAMP-2 were decreased in PD. LC3 and lysozyme levels were increased in 4-repeat tauopathy patients. EEA1 was decreased and lysozyme increased in PSP, and LAMP-1, LAMP-2, LC3 and lysozyme were increased in CBD. The lysosomal network proteins had different CSF protein profiles in all the parkinsonian syndromes, as well as in AD. It should be emphasized that only a select few of the lysosomal network proteins were observed to be changed, rather than a general change in lysosomal network proteins, which implicates the involvement of these seven proteins in specific pathological processes. The most interesting candidates, LAMP-2 and lysozyme, were selected for further study for their involvement in the pathology of AD. Lysozyme was found to co-localise with Aβ plaques in AD patients and overexpression prolonged survival and improved the activity in a Drosophila model of AD. Lysozyme was found to alter the aggregation pathway of Aβ1-42, to counteract the formation of toxic Aβ species and to protect from Aβ1-42 induced cell toxicity. Aβ1-42 in turn was found to increase the expression of lysozyme in both neuronal and glial cells. These data suggest that lysozyme levels rise in AD as a compensatory response which is protective against Aβ associated toxicity. LAMP-2 mRNA and protein were found increased in brain areas relevant for AD pathology and various cellular models showed complex involvement of LAMP-2 in Aβ related pathology, with extensive crosstalk between LAMP-2 and Aβ. Exposure to oligomeric Aβ1-42 caused an upregulation of LAMP-2 and in turn, overexpression of LAMP-2 caused a reduction in secreted levels of Aβ1-42, as well as changing the generation pattern of Aβ and affecting clearance and secretion of Aβ1-42. These data indicate that the increased levels of LAMP-2 in AD could be an attempt to regulate Aβ generation and secretion. In summary, this thesis reports that utilising lysosomal network proteins as biomarkers and novel therapeutic targets for neurodegenerative diseases holds great promise.
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Transplantation of Mouse Embryonic Stem Cell-Derived Dopaminergic Neurons in a Unilateral 6-Hydroxydopamine Lesion Rat Model of Parkinson’s Disease / Characterisation of the Fate of the Engrafted Cells and the Host Responses / Transplantation von Differenzierten embryonalen Stammzellen der Maus in ein experimentellen – 6-Hydroxydopamin-Läsion – Rattenmodell der Parkinson-Erkrankung.Thinyane, Hycianth Keneuoe 04 November 2004 (has links)
No description available.
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Precision och stabilitet vid klusilexplosionen hos patienter med Parkinsons sjukdom : En jämförelse mellan effekten av Deep Brain Stimulation i kaudala zona incerta (cZi) respektive nucleus subthalamicus (STN)Wikström, Matilda, Andersson, Julia January 2013 (has links)
Bakgrund: Deep Brain Stimulation (DBS) i nucleus subthalamicus (STN) och i kaudala zona incerta (cZi) har visat positiva effekter på motoriska symtom (rörelseförmåga och balans) vid Parkinsons sjukdom. Efter DBS har dock negativa taleffekter noterats, inklusive nedsatt artikulatorisk precision och stabilitet. Nedsatt artikulatorisk precisionoch stabilitet påverkar klusilproduktionen mest vilket kan resultera i att klusilexplosionen uteblir eller att multipla explosioner uppstår. Mål: Att undersöka artikulatorisk precision och stabilitet vid klusilexplosionen efter DBS i STN respektive cZi. Metod: I studien deltog 19 patienter varav 9 deltagare stimulerats i STN och 10 deltagare i cZi. Talinspelningar gjordes innan operation och ett år efter operation med DBSstimulering på och av. Klusilerna i talmaterialet delades in i tre kategorier, de med en klusilexplosion, de med två eller flera klusilexplosioner samt de utan klusilexplosion. Hypotesprövning gjordes gällande fördelningen av klusiler med multipla explosioner samt klusiler utan explosion mellan och inom patientgrupperna samt inom respektive klusil. Resultat: Multipla explosioner ökade hos cZi-patienterna och minskade hos STNpatienterna. Klusiler som saknade explosion ökade hos STN-patienterna medan de minskade hos cZi-patienterna. För båda patientgrupperna ökade multipla explosioner och klusiler utan explosion då stimuleringen var på jämfört med av. Skillnaderna mellan och inom grupperna var inte signifikanta. Slutsats: Artikulatorisk precision och stabilitet påverkades efter DBS i form av bristande stabilitet, för kort slutningsrörelse och felaktig koordination av slutningsrörelsen. Detta resulterade i multipla explosioner och uteblivna explosioner med olika effekter för elektrodlokalisationerna. / Background: Deep Brain Stimulation (DBS) in Subthalamicus Nucleus (STN) and Caudala zona incerta (cZi) have shown positive effects on motor symptoms in Parkinson‘s disease. Negative effects on speech after DBS has been noted including reduced articulatory precision. Reduced articulatory precision and stability affects the production of stop consonants and as a result, loss of burst or multiple burst can occur. Aim: To investigate articulatory precision and stability regarding the burst in stop consonants after DBS of STN or cZi. Method: The study included 19 patients with 9 patients stimulated in STN and 10 patientsin cZi. Speech recordings were made before surgery and one year after with stimulation ON and OFF. The stop consonants were divided into three categories, those with one burst, those with two or more bursts (multiple burst) and those with loss of burst. Hypothesis testing was done on the categorization of the stop consonants in and between the groups and between the stop consonants types. Results: Multiple burst increased in the cZi group and decreased in the STN group. Stop consonants with loss of burst increased in the STN group but decreased in the cZi group. For both groups multiple burst and stop consonants with loss of burst increased with stimulation on. The differences between and within the groups were not significant. Conclusion: Articulatory precision and stability were affected by DBS with decreased stability, shortened occlusion and incorrect coordination. As a result multiple burst and loss of burst occurred in both groups. / Speech, voice and swallowing outcomes after deep brain stimulation of the zona incerta and the pedunculopontine nucleus in Parkinson’s disease: Comparsion with stimulation of the subthalamic nucleus
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Novel sulfanyl- and sulfinylcaffeine analogues as inhibitors of monoamine oxidase / Wayne MentzMentz, Wayne January 2013 (has links)
Parkinson’s disease (PD) is a neurodegenerative disorder, which is progressive in nature and
usually associated with the elderly. It is the second most common age-related
neurodegenerative disorder after Alzheimer’s disease (AD). PD occurs when there is a dramatic
loss of dopamine (DA) in the striatum, a substructure of the basal ganglia, of the brain due to
the degeneration of the nigrostriatal pathway that contains the dopaminergic neurons. Motor
symptoms of PD include bradykinesia, muscular rigidity and resting tremors. Non-motor
symptoms include speech and sleep problems, hallucinations and depression. Diverse
treatment options are available to treat the symptoms of PD, including levodopa (L-Dopa), DA
agonists and monoamine oxidase B (MAO-B) inhibitors.
The MAOs are flavoproteins that are bound to the outer membrane of the mitochondria and
catalyze the oxidative deamination of neurotransmitters such as serotonin (5-HT), noradrenaline
(NA) and DA. Two isoforms occur, namely MAO-A and –B, which share a 70% sequence
identity. MAO-A catalyzes the oxidation of 5-HT and MAO-B has a substrate specificity towards
benzylamine and 2-phenylethylamine. DA, NA, adrenaline and tryptamine are oxidized by both
forms. MAO-A plays an important role in depression while MAO-B plays an important role in PD.
The two isoforms are not evenly distributed in the brain. Of particular relevance to PD is the
observation that, in the basal ganglia, MAO-B is the predominant form and the oxidation of DA
in this region is largely due to MAO-B activity. Also, with an increase in age, there is an up to
fourfold increase in MAO-B activity in the brain. In the aged parkinsonian brain, MAO-B is
therefore a major DA metabolizing enzyme and MAO-B inhibitors have an important role in the
therapy of PD. MAO-B inhibitors may potentially reduce the metabolic destruction of DA and
thereby provide relief from the symptoms of PD. MAO-B inhibitors may also exert a
neuroprotective effect in PD. In the catalytic cycle of MAO-B, one mole each of an aldehyde,
hydrogen peroxide and ammonia are formed for each mole of primary amine substrate oxidized.
Ferrous iron, which is abundant in the basal ganglia, may react with the hydrogen peroxide to
form hydroxyl radicals in the Fenton reaction. The hydroxyl radical damages virtually all types of
biomolecules including proteins, DNA, lipids, carbohydrates and amino acids. The aldehyde, in turn, may react with amino groups of proteins, and thus lead to cell injury. Inhibitors of MAO-B
may reduce the MAO-catalyzed formation of hydrogen peroxide and aldehydes in the basal
ganglia, and thus act as neuroprotective agents.
MAO-B inhibitors that are currently being used in the treatment of PD are selegiline and
rasagiline. Both are irreversible inhibitors of MAO-B. While irreversible inhibitors of MAO have
been used extensively as drugs, irreversible inhibition has a number of disadvantages. These
include the loss of selectivity as a result of repeated drug administration and a slow and variable
rate of enzyme recovery following termination of drug treatment. The turnover rate for the
biosynthesis of MAO-B in the human brain may require as much as 40 days while with
reversible inhibition, enzyme activity is recovered when the inhibitor is eliminated from the
tissues. For these reasons the discovery of novel MAO-B inhibitors, which interact reversibly
with the enzymes are of value in the therapy of PD.
The goal of this study was to design novel and reversible inhibitors of MAO-B, which may find
application in the therapy of PD. In the current study, caffeine was used as scaffold for the
design of new MAO inhibitors. Caffeine is reported to be a weak inhibitor of MAO-B, with an IC50
value of 5084 μM. Substitution at C-8 of the caffeine moiety, however, yields compounds with
potent MAO-B inhibitory properties. Of particular importance to this study is a recent report that
a series of 8-sulfanylcaffeine analogues acts as selective inhibitors of human MAO-B. Among
the compounds examined, 8-[(phenylethyl)sulfanyl]caffeine was found to be a particularly potent
MAO-B inhibitor with an IC50 value of 0.223 μM. In an attempt to further enhance the MAO-B
inhibition potency of 8-[(phenylethyl)sulfanyl]caffeine, and possibly to discover highly potent
MAO-B inhibitors, a series of five 8-[(phenylethyl)sulfanyl]caffeine analogues was synthesized
and evaluated as inhibitors of human MAO-A and –B. For the purpose of this study 8-
[(phenylethyl)sulfanyl]caffeine homologues containing C-3 alkyl (CF3, CH3 and OCH3) and
halogen (Cl and Br) substituents on the phenyl ring were considered. Furthermore, a series of
two 8-sulfinylcaffeine analogues and one 8-sulfonylcaffeine were synthesized and their MAO
inhibitory potencies were measured. The purpose with these compounds was to compare the
MAO inhibitory properties of the 8-sulfinylcaffeine analogues and 8-sulfonylcaffeine with those
of the 8-sulfanylcaffeine analogues. This study also investigates the MAO inhibition properties of
three selected 8-[(phenylpropyl)sulfanyl]caffeine and two 8-(benzylsulfanyl)caffeine analogues.
Chemistry: The target 8-sulfanylcaffeine analogues were synthesized according to the literature
procedure. 8-Chlorocaffeine was reacted with an appropriate mercaptan in the presence of NaOH, to yield the target 8-sulfanylcaffeine analogues in yields of 6.4–50.7%. 8-Chlorocaffeine,
in turn, was conveniently synthesized in high yield by reacting chlorine with caffeine in
chloroform. In certain instances, the mercaptan starting materials were not commercially
available and were thus synthesized according to the literature procedure by reacting an
appropriate alkylbromide with thiourea. The resulting thiouronium salt was hydrolyzed in the
presence of NaOH to yield the target mercaptan. The 8-sulfinylcaffeine analogues and 8-
sulfonylcaffeine were synthesized by reacting the 8-sulfanylcaffeines with H2O2 in the presence
of glacial acetic acid and acetic anhydride. The structures and the purities of the inhibitors were
verified by NMR, MS and HPLC analyses.
MAO inhibition studies: The MAO inhibitory properties of the test compounds were examined
using the recombinant human enzymes. The mixed MAO-A/B substrate, kynuramine, was
employed as substrate for both enzymes and the inhibition potencies were expressed as the
IC50 values.
The 8-[(phenylethyl)sulfanyl]caffeine analogues were found to be highly potent inhibitors of
MAO-B. The IC50 values recorded for these homologues ranged from 0.017–0.125 μM, making
them twofold to 13-fold more potent MAO-B inhibitors than the lead compound, 8-
[(phenylethyl)sulfanyl]caffeine (IC50 = 0.223 μM). For comparison, the reversible MAO-B
selective inhibitor, lazabemide, exhibits an IC50 value of 0.091 μM under the same conditions
(unpublished data from our laboratory). Interestingly, both alkyl (CF3, CH3 and OCH3) and
halogen (Cl and Br) substitution lead to highly potent MAO-B inhibition. It may therefore be
concluded that substitution on C-3 is a general strategy to enhance the MAO-B inhibition
potency of 8-[(phenylethyl)sulfanyl]caffeine. The results of the MAO inhibitory studies with the 8-
[(phenylpropyl)sulfanyl]caffeine analogues showed that these compounds are also inhibitors of
MAO-B with IC50 values of 0.061–0.500 μM. Those homologues substituted with chlorine on the
para and meta positions of the phenyl ring were found to be exceptionally potent inhibitors with
IC50 values of 0.061 μM and 0.062 μM, respectively. For the series of 8-
(benzylsulfanyl)caffeines, meta substitution with chlorine (IC50 = 0.227 μM) and bromine
(IC50 = 0.199 μM) was also found to enhance the MAO-B inhibition potency of 8-
(benzylsulfanyl)caffeine (IC50 = 1.86 μM). The results document that the 8-sulfinylcaffeines are
also inhibitors of MAO-B with IC50 values of 11.8–131 μM. The 8-sulfonylcaffeine was also found
to be a MAO-B inhibitor. Compared to the 8-sulfanylcaffeines, these homologues are, however,
weaker inhibitors. It may, therefore, be concluded that 8-sulfinylcaffeines and 8-sulfonylcaffeines are comparatively weak MAO-B inhibitors and less suited for the design of high potency MAO-B
inhibitors.
The results also document that the 8-[(phenylethyl)sulfanyl]caffeines are relatively weak MAO-A
inhibitors with IC50 values of 5.66–141 μM, with one homologue exhibiting no inhibition under
the experimental conditions. As evident from the selectivity indices (SI values), the 8-
[(phenylethyl)sulfanyl]caffeines were all selective inhibitors of the MAO-B isoform. Two
compounds exhibited SI values in excess of 1000. Since these compounds are also highly
potent MAO-B inhibitors, they represent suitable leads for the design of potent and selective
MAO-B inhibitors. The 8-sulfinylcaffeines and 8-sulfonylcaffeine were found to be weak MAO-A
inhibitors with IC50 values of 166–250 μM. The SI values demonstrate that these compounds are
MAO-B selective inhibitors, although to a lesser degree than the 8-
[(phenylethyl)sulfanyl]caffeines. The 8-[(phenylpropyl)sulfanyl]caffeines are also MAO-A
inhibitors with IC50 values of 0.708–6.48 μM. It is noteworthy that these homologues are the
most potent MAO-A inhibitors among the compounds evaluated in this study. In fact, one of the
8-[(phenylpropyl)sulfanyl]caffeines, 8-{[3-(4-chlorophenyl)propyl]sulfanyl}caffeine (IC50 = 0.708
μM), is the only compound with an IC50 value for the inhibition of MAO-A in the submicromolar
range. The 8-[(phenylpropyl)sulfanyl]caffeines display, in general, lower degrees of selectivity
for MAO-B than the corresponding 8-[(phenylethyl)sulfanyl]caffeines.
Reversibility studies: The reversibility of the interaction of a representative inhibitor, 8-{[2-(3-
(trifluoromethyl)phenyl)ethyl]sulfanyl}caffeine, with MAO-B was investigated by evaluating the
recovery of the enzymatic activity after dilution of the enzyme-inhibitor complex. For this
purpose, MAO-B was preincubated with the test compound at concentrations of 10 × IC50 and
100 × IC50 for 30 min. The reactions were subsequently diluted 100-fold to 0.1 × IC50 and 1 ×
IC50, respectively. The results show that, after dilution to 0.1 × IC50 and 1 × IC50, the MAO-B
catalytic activities are recovered to 35% and 22%, respectively, of the control value. For
reversible enzyme inhibition, the enzyme activities are expected to recover to levels of
approximately 90% and 50%, respectively, after 100-fold dilution of the preincubations
containing inhibitor concentrations of 10 × IC50 and 100 × IC50. After preincubation of MAO-B
with the irreversible inhibitor (R)-deprenyl (at 10 × IC50), and dilution of the resulting complex to
0.1 × IC50, MAO-B activity is not recovered (3.0% of control). These data indicate that the test
compound does indeed react reversibly with MAO-B but because enzyme activities are not
recovered to the expected 90% and 50% respectively, it may suggest that the test compound
possess a quasi-reversible or tight-binding component. Hansch-type structure activity relationship studies: A limited Hansch-type QSAR study was
performed for the inhibition of MAO by the 8-[(phenylethyl)sulfanyl]caffeines. For this purpose,
five parameters were used to describe the physicochemical properties of the C-3 substituents
on the phenyl rings of the inhibitors. The Van der Waals volume (Vw) and Taft steric parameter
(Es) served as descriptors of the bulkiness of the substituents, while the lipophilicities were
described by the Hansch constant (π). The electronic properties were described by the classical
Hammett constant (σm) and the Swain-Lupton constant (F). A one-parameter fit with the Taft
steric parameter versus the inhibition potency (logIC50) yielded the best correlation with a
correlation coefficient (R2) of 0.912 and a statistical F value of 41.27 (Fmax = 35). The positive
sign of the Es (+0.47) parameter coefficient indicated that the inhibition potencies of the 8-
[(phenylethyl)sulfanyl]caffeines towards MAO-B may be enhanced by substitution with sterically
large groups at C-3 of the phenyl rings of the inhibitors. / Thesis (MSc (Pharmaceutical Chemistry))--North-West University, Potchefstroom Campus, 2013
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Aminopyrimidine derivatives as adenosine antagonists / Janke KleynhansKleynhans, Janke January 2013 (has links)
Aims of this project - The aim of this study was to design and synthesise novel 2-aminopyrimidine derivatives as potential adenosine A1 and A2A receptor antagonists.
Background and rationale - Parkinson’s disease is the second most common neurodegenerative disorder (after
Alzheimer’s disease) and is characterised by the selective death of the dopaminergic
neurons of the nigro-striatal pathway. Distinctive motor symptoms include bradykinesia,
muscle rigidity and tremor, while non-motor symptoms, of which cognitive dysfunction is an
example, also frequently occur. Current therapy provides symptomatic relief mainly by
augmentation of dopaminergic signalling (levodopa, dopamine agonists, MAO and COMT
enzyme inhibitors), but disease progression is not adequately addressed. New therapies that
can prevent further neurodegeneration in addition to providing symptomatic relief are
therefore urgently required.
Adenosine has an important function as neuromodulator in the central nervous system. The
adenosine A2A receptor in particular plays an essential role in the regulation of movement.
This, coupled to the fact that it is uniquely distributed in the basal ganglia, contributes to its
attractiveness as non-dopaminergic target in the treatment of movement disorders, such as
Parkinson’s disease. The efficacy of adenosine receptor antagonists has been illustrated in
animal models of Parkinson’s disease and several adenosine receptor antagonists have also
reached clinical trials. The neuroprotective properties of adenosine A2A receptor antagonists
are further attributed to their ability to modulate neuro-inflammation and decrease the
release of the excitatory neurotransmitter glutamate, which is implicated in neurotoxicity.
While adenosine A1 receptor antagonism has a synergistic effect on the motor effects of
adenosine A2A receptor antagonism, it has the additional benefit of improving cognitive dysfunction, a cardinal non-motor symptom of Parkinson’s disease. Dual antagonism of
adenosine A1 and A2A receptors therefore offers the potential of providing symptomatic relief
as well as the neuroprotection so desperately needed in the clinical environment.
Amino substituted heterocyclic scaffolds, such as those containing the 2-aminopyrimidine
motif, have been shown to exhibit good efficacy as dual adenosine receptor antagonists.
Since the structure activity relationships of 2-aminopyrimidines have not been
comprehensively explored, it is in this regard that this study aimed to make a contribution.
Results - Fourteen 2-aminopyrimidines were synthesised successfully over three steps, (although in
low yields) and characterised by nuclear magnetic resonance and infrared spectroscopy,
mass spectrometry, by determination of melting points and high performance liquid
chromatography. Structure modifications explored included variation of the aromatic
substituent on position 4, as well as variations in the substituents of the phenyl ring, present
on position 6 of the pyrimidine ring.
Radioligand binding assays were performed to determine the affinities of the synthesised
compounds for the adenosine A1 and A2A receptor subtypes. Several high dual affinity
derivatives were identified during this study; the compound with the highest affinity was 4-(5-
methylthiophen-2-yl)-6-[3-(piperidine-1-carbonyl)phenyl]pyrimidin-2-amine (39f) with Ki
values of 0.5 nM and 2.3 nM for the adenosine A2A and adenosine A1 receptors,
respectively.
A few general structure activity relationships were derived, which included: The effect of the
aromatic substituent (position 4) on A2A affinity could be summarised (in order of declining
affinity) as follows: 5-methylthiophene > phenyl > furan > pyridine > p-fluorophenyl >
benzofuran. On the other hand, the effect of this substituent on A1 receptor affinity could be
summarised (in order of declining affinity) as follows: phenyl > 5-methylthiophene > pfluorophenyl
> benzofuran > pyridine. The affinities as exhibited by the methylthiophene
derivatives 39f, 39h – 39j, further showed that while piperidine substitution (39f) resulted in
optimal A2A and A1 affinity, pyrrolidine substitution (39j) was less favourable. Substitution at
the 4ʹ position of the phenyl ring, as well as thiazole substitution, generally resulted in poor
adenosine A1 and A2A receptor affinity. However, 4-[2-amino-6-(5-methylfuran-2-yl)pyrimidin-
4-yl]-N-(1,3-benzothiazol-2-yl)benzamide (39l) surprisingly demonstrated good affinity and
selectivity for the adenosine A1 receptor. The results obtained during radioligand binding assays were rationalised by QSAR and
molecular modelling (Discovery Studio 3.1, Accelrys) studies. The inverse relationship seen
between log Ki (as indicator of affinity) and polar surface area, illustrated the importance of
this physico-chemical property in the design of 2-aminopyrimidine A2A antagonists. The
results from the docking study further showed that the orientation adopted by derivatives in
the binding cavity (and particular hydrogen bonding to Asn 253 and Glu 169) is of
importance. Results from the MTT cell viability assay indicated that none of the high affinity
derivatives had a significant effect on cell viability at 1 μM, a concentration much higher than
their Ki values. However, incorporation of the furan, benzofuran and p-fluorophenyl groups
as aromatic substituent and a pyrrolidine as amine substituent, presented liabilities.
Lastly, the haloperidol induced catalepsy assay (in rats) was used to give a preliminary
indication of adenosine receptor antagonism or agonism. Compound 39f failed to reverse
catalepsy under standard conditions, but showed some reversal after an increased time
period. Indications therefore exist that 39f is an adenosine receptor antagonist that suffers
from bioavailability issues. Compound (39c), 4-phenyl-6-[3-(piperidine-1-
carbonyl)phenyl]pyrimidin-2-amine which also demonstrated promising affinity in the
radioligand binding assays however showed a statistically significant reduction in catalepsy,
indicating adenosine A2A receptor antagonism, and in vivo efficacy.
Highly potent, dual affinity aminopyrimidine derivatives with acceptable toxicity profiles were
identified in this study, with compound 39c demonstrating in vivo activity. The aim of
designing and synthesising a promising dual adenosine A1/A2A receptor antagonist is
therefore realised, with compound 39c as the most favourable example. / MSc (Pharmaceutical Chemistry), North-West University, Potchefstroom Campus, 2014
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Novel sulfanyl- and sulfinylcaffeine analogues as inhibitors of monoamine oxidase / Wayne MentzMentz, Wayne January 2013 (has links)
Parkinson’s disease (PD) is a neurodegenerative disorder, which is progressive in nature and
usually associated with the elderly. It is the second most common age-related
neurodegenerative disorder after Alzheimer’s disease (AD). PD occurs when there is a dramatic
loss of dopamine (DA) in the striatum, a substructure of the basal ganglia, of the brain due to
the degeneration of the nigrostriatal pathway that contains the dopaminergic neurons. Motor
symptoms of PD include bradykinesia, muscular rigidity and resting tremors. Non-motor
symptoms include speech and sleep problems, hallucinations and depression. Diverse
treatment options are available to treat the symptoms of PD, including levodopa (L-Dopa), DA
agonists and monoamine oxidase B (MAO-B) inhibitors.
The MAOs are flavoproteins that are bound to the outer membrane of the mitochondria and
catalyze the oxidative deamination of neurotransmitters such as serotonin (5-HT), noradrenaline
(NA) and DA. Two isoforms occur, namely MAO-A and –B, which share a 70% sequence
identity. MAO-A catalyzes the oxidation of 5-HT and MAO-B has a substrate specificity towards
benzylamine and 2-phenylethylamine. DA, NA, adrenaline and tryptamine are oxidized by both
forms. MAO-A plays an important role in depression while MAO-B plays an important role in PD.
The two isoforms are not evenly distributed in the brain. Of particular relevance to PD is the
observation that, in the basal ganglia, MAO-B is the predominant form and the oxidation of DA
in this region is largely due to MAO-B activity. Also, with an increase in age, there is an up to
fourfold increase in MAO-B activity in the brain. In the aged parkinsonian brain, MAO-B is
therefore a major DA metabolizing enzyme and MAO-B inhibitors have an important role in the
therapy of PD. MAO-B inhibitors may potentially reduce the metabolic destruction of DA and
thereby provide relief from the symptoms of PD. MAO-B inhibitors may also exert a
neuroprotective effect in PD. In the catalytic cycle of MAO-B, one mole each of an aldehyde,
hydrogen peroxide and ammonia are formed for each mole of primary amine substrate oxidized.
Ferrous iron, which is abundant in the basal ganglia, may react with the hydrogen peroxide to
form hydroxyl radicals in the Fenton reaction. The hydroxyl radical damages virtually all types of
biomolecules including proteins, DNA, lipids, carbohydrates and amino acids. The aldehyde, in turn, may react with amino groups of proteins, and thus lead to cell injury. Inhibitors of MAO-B
may reduce the MAO-catalyzed formation of hydrogen peroxide and aldehydes in the basal
ganglia, and thus act as neuroprotective agents.
MAO-B inhibitors that are currently being used in the treatment of PD are selegiline and
rasagiline. Both are irreversible inhibitors of MAO-B. While irreversible inhibitors of MAO have
been used extensively as drugs, irreversible inhibition has a number of disadvantages. These
include the loss of selectivity as a result of repeated drug administration and a slow and variable
rate of enzyme recovery following termination of drug treatment. The turnover rate for the
biosynthesis of MAO-B in the human brain may require as much as 40 days while with
reversible inhibition, enzyme activity is recovered when the inhibitor is eliminated from the
tissues. For these reasons the discovery of novel MAO-B inhibitors, which interact reversibly
with the enzymes are of value in the therapy of PD.
The goal of this study was to design novel and reversible inhibitors of MAO-B, which may find
application in the therapy of PD. In the current study, caffeine was used as scaffold for the
design of new MAO inhibitors. Caffeine is reported to be a weak inhibitor of MAO-B, with an IC50
value of 5084 μM. Substitution at C-8 of the caffeine moiety, however, yields compounds with
potent MAO-B inhibitory properties. Of particular importance to this study is a recent report that
a series of 8-sulfanylcaffeine analogues acts as selective inhibitors of human MAO-B. Among
the compounds examined, 8-[(phenylethyl)sulfanyl]caffeine was found to be a particularly potent
MAO-B inhibitor with an IC50 value of 0.223 μM. In an attempt to further enhance the MAO-B
inhibition potency of 8-[(phenylethyl)sulfanyl]caffeine, and possibly to discover highly potent
MAO-B inhibitors, a series of five 8-[(phenylethyl)sulfanyl]caffeine analogues was synthesized
and evaluated as inhibitors of human MAO-A and –B. For the purpose of this study 8-
[(phenylethyl)sulfanyl]caffeine homologues containing C-3 alkyl (CF3, CH3 and OCH3) and
halogen (Cl and Br) substituents on the phenyl ring were considered. Furthermore, a series of
two 8-sulfinylcaffeine analogues and one 8-sulfonylcaffeine were synthesized and their MAO
inhibitory potencies were measured. The purpose with these compounds was to compare the
MAO inhibitory properties of the 8-sulfinylcaffeine analogues and 8-sulfonylcaffeine with those
of the 8-sulfanylcaffeine analogues. This study also investigates the MAO inhibition properties of
three selected 8-[(phenylpropyl)sulfanyl]caffeine and two 8-(benzylsulfanyl)caffeine analogues.
Chemistry: The target 8-sulfanylcaffeine analogues were synthesized according to the literature
procedure. 8-Chlorocaffeine was reacted with an appropriate mercaptan in the presence of NaOH, to yield the target 8-sulfanylcaffeine analogues in yields of 6.4–50.7%. 8-Chlorocaffeine,
in turn, was conveniently synthesized in high yield by reacting chlorine with caffeine in
chloroform. In certain instances, the mercaptan starting materials were not commercially
available and were thus synthesized according to the literature procedure by reacting an
appropriate alkylbromide with thiourea. The resulting thiouronium salt was hydrolyzed in the
presence of NaOH to yield the target mercaptan. The 8-sulfinylcaffeine analogues and 8-
sulfonylcaffeine were synthesized by reacting the 8-sulfanylcaffeines with H2O2 in the presence
of glacial acetic acid and acetic anhydride. The structures and the purities of the inhibitors were
verified by NMR, MS and HPLC analyses.
MAO inhibition studies: The MAO inhibitory properties of the test compounds were examined
using the recombinant human enzymes. The mixed MAO-A/B substrate, kynuramine, was
employed as substrate for both enzymes and the inhibition potencies were expressed as the
IC50 values.
The 8-[(phenylethyl)sulfanyl]caffeine analogues were found to be highly potent inhibitors of
MAO-B. The IC50 values recorded for these homologues ranged from 0.017–0.125 μM, making
them twofold to 13-fold more potent MAO-B inhibitors than the lead compound, 8-
[(phenylethyl)sulfanyl]caffeine (IC50 = 0.223 μM). For comparison, the reversible MAO-B
selective inhibitor, lazabemide, exhibits an IC50 value of 0.091 μM under the same conditions
(unpublished data from our laboratory). Interestingly, both alkyl (CF3, CH3 and OCH3) and
halogen (Cl and Br) substitution lead to highly potent MAO-B inhibition. It may therefore be
concluded that substitution on C-3 is a general strategy to enhance the MAO-B inhibition
potency of 8-[(phenylethyl)sulfanyl]caffeine. The results of the MAO inhibitory studies with the 8-
[(phenylpropyl)sulfanyl]caffeine analogues showed that these compounds are also inhibitors of
MAO-B with IC50 values of 0.061–0.500 μM. Those homologues substituted with chlorine on the
para and meta positions of the phenyl ring were found to be exceptionally potent inhibitors with
IC50 values of 0.061 μM and 0.062 μM, respectively. For the series of 8-
(benzylsulfanyl)caffeines, meta substitution with chlorine (IC50 = 0.227 μM) and bromine
(IC50 = 0.199 μM) was also found to enhance the MAO-B inhibition potency of 8-
(benzylsulfanyl)caffeine (IC50 = 1.86 μM). The results document that the 8-sulfinylcaffeines are
also inhibitors of MAO-B with IC50 values of 11.8–131 μM. The 8-sulfonylcaffeine was also found
to be a MAO-B inhibitor. Compared to the 8-sulfanylcaffeines, these homologues are, however,
weaker inhibitors. It may, therefore, be concluded that 8-sulfinylcaffeines and 8-sulfonylcaffeines are comparatively weak MAO-B inhibitors and less suited for the design of high potency MAO-B
inhibitors.
The results also document that the 8-[(phenylethyl)sulfanyl]caffeines are relatively weak MAO-A
inhibitors with IC50 values of 5.66–141 μM, with one homologue exhibiting no inhibition under
the experimental conditions. As evident from the selectivity indices (SI values), the 8-
[(phenylethyl)sulfanyl]caffeines were all selective inhibitors of the MAO-B isoform. Two
compounds exhibited SI values in excess of 1000. Since these compounds are also highly
potent MAO-B inhibitors, they represent suitable leads for the design of potent and selective
MAO-B inhibitors. The 8-sulfinylcaffeines and 8-sulfonylcaffeine were found to be weak MAO-A
inhibitors with IC50 values of 166–250 μM. The SI values demonstrate that these compounds are
MAO-B selective inhibitors, although to a lesser degree than the 8-
[(phenylethyl)sulfanyl]caffeines. The 8-[(phenylpropyl)sulfanyl]caffeines are also MAO-A
inhibitors with IC50 values of 0.708–6.48 μM. It is noteworthy that these homologues are the
most potent MAO-A inhibitors among the compounds evaluated in this study. In fact, one of the
8-[(phenylpropyl)sulfanyl]caffeines, 8-{[3-(4-chlorophenyl)propyl]sulfanyl}caffeine (IC50 = 0.708
μM), is the only compound with an IC50 value for the inhibition of MAO-A in the submicromolar
range. The 8-[(phenylpropyl)sulfanyl]caffeines display, in general, lower degrees of selectivity
for MAO-B than the corresponding 8-[(phenylethyl)sulfanyl]caffeines.
Reversibility studies: The reversibility of the interaction of a representative inhibitor, 8-{[2-(3-
(trifluoromethyl)phenyl)ethyl]sulfanyl}caffeine, with MAO-B was investigated by evaluating the
recovery of the enzymatic activity after dilution of the enzyme-inhibitor complex. For this
purpose, MAO-B was preincubated with the test compound at concentrations of 10 × IC50 and
100 × IC50 for 30 min. The reactions were subsequently diluted 100-fold to 0.1 × IC50 and 1 ×
IC50, respectively. The results show that, after dilution to 0.1 × IC50 and 1 × IC50, the MAO-B
catalytic activities are recovered to 35% and 22%, respectively, of the control value. For
reversible enzyme inhibition, the enzyme activities are expected to recover to levels of
approximately 90% and 50%, respectively, after 100-fold dilution of the preincubations
containing inhibitor concentrations of 10 × IC50 and 100 × IC50. After preincubation of MAO-B
with the irreversible inhibitor (R)-deprenyl (at 10 × IC50), and dilution of the resulting complex to
0.1 × IC50, MAO-B activity is not recovered (3.0% of control). These data indicate that the test
compound does indeed react reversibly with MAO-B but because enzyme activities are not
recovered to the expected 90% and 50% respectively, it may suggest that the test compound
possess a quasi-reversible or tight-binding component. Hansch-type structure activity relationship studies: A limited Hansch-type QSAR study was
performed for the inhibition of MAO by the 8-[(phenylethyl)sulfanyl]caffeines. For this purpose,
five parameters were used to describe the physicochemical properties of the C-3 substituents
on the phenyl rings of the inhibitors. The Van der Waals volume (Vw) and Taft steric parameter
(Es) served as descriptors of the bulkiness of the substituents, while the lipophilicities were
described by the Hansch constant (π). The electronic properties were described by the classical
Hammett constant (σm) and the Swain-Lupton constant (F). A one-parameter fit with the Taft
steric parameter versus the inhibition potency (logIC50) yielded the best correlation with a
correlation coefficient (R2) of 0.912 and a statistical F value of 41.27 (Fmax = 35). The positive
sign of the Es (+0.47) parameter coefficient indicated that the inhibition potencies of the 8-
[(phenylethyl)sulfanyl]caffeines towards MAO-B may be enhanced by substitution with sterically
large groups at C-3 of the phenyl rings of the inhibitors. / Thesis (MSc (Pharmaceutical Chemistry))--North-West University, Potchefstroom Campus, 2013
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Protein Structure Characterization by Solid-State NMR: Structural Comparison of Mouse and Human alpha-Synuclein Fibrils, Sparse 13C Labeling Schemes, and Stereospecific Assignment of Val and Leu Prochiral Methyl GroupsLv, Guohua 28 March 2013 (has links)
No description available.
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Generation of human dopaminergic neurons from induced pluripotent stem cells to model Parkinson's diseaseSánchez Danés, Adriana, 1984- 21 May 2012 (has links)
Parkinson’s disease (PD) is an incurable, chronically progressive neurodegenerative disease leading to premature invalidity and death. The locomotor disability of PD patients is mainly rooted in the gradual and insidious degeneration of dopaminergic neurons (DA) projecting from the midbrain substantia nigra (SN) to the basal ganglia striatum, a pathological process highlighted microscopically by the formation of insoluble cytosolic protein aggregates, known as Lewy bodies and Lewy neurites. The pathogenic mechanisms leading to PD remain poorly understood, arguably owing to the lack of suitable animal and cellular experimental models of the disease. Therefore, there is an urgent need for developing reliable experimental models that recapitulate the key features of PD. The recent development of induced pluripotent stem cell (iPSC) technology has enabled the generation of patient-specific iPSC and their use to model human diseases, although it is currently unclear whether this approach could be useful to successfully model age-related conditions. Importantly, disease modeling using iPSC largely relies on the existence of efficient protocols for the differentiation of disease-relevant cell types. Here, we first developed an efficient protocol for the differentiation of iPSC to authentic midbrain-specific DA neurons with SN properties by forced expression of LMX1A using a lentivirus-mediated gene delivery system. Next, we generated an iPSC-based cellular model of PD that recapitulates key phenotypic features of PD, such as DA neuron loss and α-synuclein accumulation in DA neurons from PD patients. Overall, our results demonstrate that we have developed a valuable tool for elucidating the pathogenic mechanisms leading to PD, as well as an experimental platform for screening new drugs that may prevent or rescue neurodegeneration in PD. / La malaltia de Parkinson (MP) és una malaltia neurodegenerativa incurable que causa invalidesa i mort prematura. Els pacients de la malaltia de Parkinson presenten alteracions motores degudes a una degeneració gradual de les neurones dopaminèrgiques que projecten des de la substància nigra fins a l’estriat. A nivell microscòpic s’observa la presència d’agregats proteics insolubles en el citosol de les neurones coneguts com cossos o neurites de Lewy. Els mecanismes patològics responsables de la MP no es coneixen bé, possiblement a causa de la manca de models animals i cel•lulars adequats. Per tant, existeix una gran necessitat de desenvolupar models experimentals fiables que recapitulin les característiques bàsiques de la MP. El recent desenvolupament de les cèl•lules mare pluripotents induïdes (iPSC) ha permès la generació de iPSC específiques de pacient i el seu ús per modelar malalties humanes, ara bé, no és clar si aquesta estratègia es pot utilitzar per modelar exitosament malalties d’origen tardà, com ara la MP. És important destacar que el modelatge de malalties utilitzant iPSC, es basa, en gran mesura en l'existència de protocols eficients per a la diferenciació de les iPSC cap al tipus cel•lular rellevant per a la malaltia. Durant aquest període, per primera vegada, s’ha desenvolupat un protocol per a l’eficient diferenciació de les iPSC cap a neurones dopaminèrgiques amb les propietats característiques de neurones dopaminèrgiques nigrostriatals, mitjançant l’expressió forçada de LMX1A utilitzant vectors lentivirals. A continuació, s’ha generat un model cel•lular usant iPSC derivades de pacients de MP que recapitula les principals característiques fenotípiques de la malaltia, com ara la pèrdua de neurones dopaminèrgiques i l'acumulació de α-sinucleïna en les neurones dopaminèrgiques. En general, els nostres resultats demostren que hem desenvolupat una eina valuosa per a l’estudi dels mecanismes patològics que condueixen a la MP, així com una nova plataforma pel descobriment de nous fàrmacs encaminats a prevenir o evitar la neurodegeneració.
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Efeito de um programa sistematizado de atividades rítmicas e dança nas funções cognitivas, aspectos neuropsiquiátricos e andar de pacientes com doença de Parkinson: um estudo controlado e randomizado / Effects of systematized rhythmic activities and dance program on cognitive function, neuropsychiatric aspects and gait of patients with Parkinson disease: a randomized controlled trialLirani-Silva, Ellen [UNESP] 03 July 2018 (has links)
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Previous issue date: 2018-07-03 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Introdução: A presente tese de Doutorado é composta por dois estudos. O objetivo do Estudo #1 foi investigar a associação entre domínios do andar (com e sem tarefa dupla) e domínios cognitivos e neuropsiquiátricos de pacientes com DP (DP). O objetivo do Estudo #2 foi investigar os efeitos de uma intervenção de atividades rítmicas e dança no andar, funções cognitivas e aspectos neuropsiquiátricos de pacientes com DP e a manutenção de benefícios após um período de follow up (5 meses). Materiais e método: O Estudo #1 contou com a participação de 87 pacientes com DP. Após avaliação clínica e anamnese, os pacientes foram avaliados quanto ao andar (com e sem tarefa dupla), funções cognitivas e aspectos neuropsiquiátricos. A partir das avaliações, dois modelos foram elaborados: i) modelo do andar formado por 16 características espaço-temporais do andar, distribuídos em cinco domínios (pace, variabilidade, ritmo, assimetria e controle postural); ii) modelo de aspectos cognitivos e neuropsiquiátricos formado por 10 testes, distribuídos em sete domínios (cognição global, memória, função executiva, atenção, memória de trabalho, habilidade visuoespacial, neuropsiquiátrico ). O Estudo #2 contou com a participação de 86 pacientes com DP que foram distribuídos randomicamente em dois grupos: grupo de atividades rítmicas (DPd) e dança e grupo convívio (DPc). As atividades do grupo DPd foram realizadas com base em diferentes estilos, com progressão tanto em mudanças do ambiente como em complexidade dos movimentos. O grupo DPc participou de atividades divididas em três etapas: i) palestras e discussões sobre a DP, sem nenhuma sobrecarga cognitiva e motora; ii) atividades de voz; iii) atividades de disfagia. Ambas as intervenções ocorreram durante 6 meses, 3 vezes por semana, com 1 hora por sessão. O mesmo protocolo de avaliações do Estudo #1 foi utilizado no Estudo #2. As avaliações foram conduzidas, antes e após o período de intervenção (6 meses), e 5 meses após um período sem intervenção. Resultados (Estudo #1): Foram verificadas associações entre domínios cognitivos e do andar, especialmente entre o domínio pace, cognição global, atenção e memória. Ainda, foi verificada uma maior capacidade de predição do domínio pace em condição de tarefa dupla, onde os domínios cognição global e atenção, juntamente com as variáveis de controle do estudo, explicaram em 42% da variância dos dados. Resultados (Estudo #2): Os pacientes do grupo DPd apresentaram diminuição da assimetria durante o andar livre no momento follow up em comparação ao momento pós. Ainda, a intervenção de atividades rítmicas e dança foi capaz de evitar a progressão de características do andar com tarefa dupla relacionada ao domínio pace, enquanto os pacientes do grupo DPc apresentaram piora dessas características ao longo do estudo. Quanto aos aspectos cognitivos, foi observada piora na atenção dos pacientes do grupo DPc, mas não para o grupo DPd. No entanto, apenas o grupo DPc apresentou benefícios na cognição global. Conclusão: Domínios do andar estão associados a domínios cognitivos de pacientes com DP, mas, para o presente estudo, não com domínios neuropsiquiátricos. O domínio pace (andar com tarefa dupla) apresentou o melhor modelo preditivo do estudo, que foi composto pelos domínios cognição global e atenção. Em relação a intervenção proposta no Estudo #2, a intervenção de atividades rítmicas e dança é capaz de beneficiar características discretas do andar e promover a manutenção de alguns aspectos do andar, cognitivos e neuropsiquiátricos. / Introduction: This PhD thesis consists of two studies. The aim of the Study #1 was to investigate the association between gait domains (with and without dual task) and cognitive and neuropsychiatric domains of patients with Parkinson’s disease (PD). The aim of the St udy #2 was to investigate the effects of a rhythm activities and dance intervention on gait, cognitive function and neuropsychiatric aspects of patients with PD, as well as the retention of benefits after a follow up period (5 months). Methods: Study #1 in volved the participation of 87 patients with PD. A fter clinical assessment, gait (with and without dual task), cognition and neuropsychiatric aspects were assessed. Gait, cognition and neuropsychiatric aspects were summarized in two models: i) a gait model with 16 spatial - temporal gait characteristics, described by five domains (pace, variability, rhythm, asymmetry and postural control); ii) a cognitive and neuropsychiatric model with 10 assessments organized in seven domains (global cognition, memory, exec utive function, attention, working memory, visuospatial ability and neuropsychiatric). Study #2 involved 86 patients with PD which were allocated in two groups: rhythm activities and dance intervention group (PDd) and socializing group (PDs). Activities of the PDd group were structured based on different styles of dance, with progression in the environment and movement complexity. Activities of t he PDs group were organized in three phases: i) talks and discussion about PD, with low cognitive or motor impact ; ii) voice activities; iii) activities focused in dysphagia. Both interventions were conducted during 6 months, three time s per week, one hour per session. The testing protocol of Study #2 was the same of the Study #1. All assessments were conducted befor e, immediately after the intervention and after a 5 - month follow up. Results (Study 1): Cognitive domains were associated with gait, specially between pace domain and global cognition, attention and memory domain s . Also, a great capacity of prediction was observed for pace domain under dual task , where global cognition and attention, with control variables , explained 42% of the data variance. Results (Study #2): There was a decrease in gait asymmetry (without dual task) at follow up moment compare d to post intervention for the PDd group. Also, the intervention of rhythm activities and dance was effective to prevent the progression of gait with dual task, specially related to pace domain. The PDs group worsened these gait characteristics during the study. In relation to cognitive aspects, the PDs, but not the PDd, worsened attention. Also, the PDs improved global cognition. Conclusion: Gait d omains are associated to cognitive domains in patients with PD, but not to neuropsychiatric domain. Pace domain (with du al task) had the best predictive model of the study, which was composed by global cognition and attention domains. The rhythm activities and dance intervention was effective to benefit discreet gait characteristics and prevent the progression of some gait, cognitive and neuropsychiatric aspects.
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