Peroxiredoxin 6 in human brain: molecular forms, cellular distribution and association with Alzheimer's disease pathology

Peroxiredoxin 6 is an antioxidant enzyme and is the 1-cys member of the peroxiredoxin family. Using two-dimensional electrophoresis and Western blotting, we have shown for the first time that, in human control and brain tissue of patient’s with Alzheimer’s disease (AD), this enzyme exists as three major and five minor forms with pIs from 5.3 to 6.1. Using specific cellular markers, we have shown that peroxiredoxin 6 is present in astrocytes with very low levels in neurons, but not detectable in microglia or oligodendrocytes. In control brains, there was a very low level of peroxiredoxin 6 staining in astrocytes that was confined to a “halo” around the nucleus. In AD, there were marked increases in the number and staining intensity of peroxiredoxin 6 positive astrocytes in both gray and white matter in the midfrontal cortex, cingulate, hippocampus and amygdala. Confocal microscopy using antibodies to Aβ peptide, tau and peroxiredoxin 6 showed that peroxiredoxin 6 positive astrocytes are closely involved with diffuse plaques and to a lesser extent with neuritic plaques, suggesting that plaques are producing reactive oxygen species. There appeared to be little astrocytic response to tau containing neurons. Although peroxiredoxin 6 positive astrocytes were seen to make multiple contacts with tau positive neurons, there was no intraneuronal colocalization. In brain tissue of patients with AD, many blood vessels exhibited peroxiredoxin 6 staining that appeared to be due to the astrocytic foot processes. These results suggest that oxidative stress conditions exist in AD and that peroxiredoxin 6 is an important antioxidant enzyme in human brain defenses.

Reasons for admission to hospital for Parkinson's disease

The management of Parkinson's disease (PD) tends to focus on the presenting motor syndrome; yet, in the long term, nonmotor complications of the illness and complications of treatment become increasingly troublesome. The aims of this study were to review the reasons for 761 hospital admissions for patients with a diagnosis of PD and to determine the cause of hospitalization. Only 15% were admitted for primary management of the motor syndrome. PD was the secondary diagnosis in 645 admissions. Of the latter, 39% were admitted because of falls leading to fracture, pneumonia, encephalopathy or dementia and hypotension with syncope. Cardiac and gastrointestinal diseases accounted for a further 22% of admissions. Complications of the later stages of PD and associated treatments are more likely to lead to hospital admission than management of the primary motor syndrome. Some of the emergency hospital admissions for PD may be potentially avoidable with better planning of management in the outpatient and community setting.

Risperidone versus pimozide in Tourette's disorder: a comparative double-blind parallel-group study

BACKGROUND

The treatment of Tourette's disorder with classical neuroleptics is limited by their side effects. Risperidone is a new efficacious antipsychotic with a low propensity for extrapyramidal side effects. To establish risperidone's therapeutic potential in Tourette's disorder, we studied the safety and efficacy of risperidone in comparison with pimozide in patients with Tourette's disorder diagnosed according to DSM-III-R.

METHOD

In a 12-week, multicenter, double-blind, parallel-group study, 26 patients were treated with risperidone (mean daily dose = 3.8 mg), and 24 patients were treated with pimozide (mean daily dose = 2.9 mg).

RESULTS

There was significant improvement of tics with respect to the Tourette's Symptom Severity Scale (TSSS) for both groups. Forty-one patients completed the study. At endpoint, 54% (14/26) of the risperidone patients and 38% (9/24) of the pimozide patients had only very mild or no symptoms on the global severity rating of the TSSS. Both treatment groups had improved significantly at endpoint in regard to Global Assessment of Functioning and Clinical Global Impressions scale outcomes. Symptoms of anxiety and depressive mood improved significantly from baseline in both groups. Obsessive-compulsive behavior improvement reached significance only in the risperidone group. Although the severity of extrapyramidal side effects was low in both groups, fewer patients in the risperidone group reported extrapyramidal side effects (N = 4) compared with the pimozide group (N = 8). Depression, fatigue, and somnolence were reported as the most prominent side effects in both treatment groups.

CONCLUSION

Both drugs were efficacious and well tolerated in patients with Tourette's disorder. Risperidone may become the first-line drug in the treatment of Tourette's disorder owing to a more favorable efficacy and tolerability profile.

Utilisation of predictive, prenatal and diagnostic testing for Huntington's disease in Johannesburg

CONTEXT

Huntington's disease (HD) is a dominantly inherited condition in which the gene defect is known. As such individuals in at-risk families can be tested before symptoms occur, prenatally, or after symptoms appear to confirm the diagnosis.

OBJECTIVES

To investigate the utilisation and sequelae of the predictive, prenatal and diagnostic services offered to families with suspected Huntington's disease.

DESIGN

A retrospective design was used. The 1975-1997 records of the Department of Human Genetics for all families with a history of HD presenting for genetic counselling and DNA analysis were studied.

SETTING

Department of Human Genetics, South African Institute for Medical Research and University of the Witwatersrand, Johannesburg.

SUBJECTS

There were 30 at-risk (50% risk) subjects for predictive testing, 7 women (10 pregnancies) for prenatal testing, and 52 subjects for diagnostic testing.

OUTCOME MEASURES

These were provided by the results from molecular studies and by the action taken by subjects after a predictive or prenatal result was given.

RESULTS

Altogether 15 (50%) subjects for predictive testing had a positive result, but none had serious psychiatric sequelae. Two women were found to be carrying an affected fetus and both requested pregnancy termination. Of 52 diagnostic tests, 33 (63%) were positive.

CONCLUSION

The service was used appropriately, and there were no traumatic incidents following positive results. There was no genotypic or sex bias in subjects presenting for testing. Black and white patients were equally likely to be positive for HD on diagnostic testing. The families appreciated the service and found it useful in the detection and prevention of HD.

Huntington's disease confirmed by genetic testing in five African families

Huntington's disease is an autosomal-dominant inherited progressive neurodegenerative disease associated with an expanded trinucleotide repeat (CAG) sequence on the short arm of chromosome 4. The disease is considered rare in Africans. We report five black South African families of different ethnic origin with proven expansions typical of Huntington's disease and discuss the possible origins of the disease in Africa.

Neuro-acanthocytosis--a rare cause of chorea

Neuro-acanthocytosis is a rare neurological disorder characterised by stereotyped chorea, especially of the mouth, areflexia and acanthocytes seen in the peripheral blood. No cases have been described in the literature from South Africa. We report here a case of neuro-acanthocytosis seen in a black woman who presented to Johannesburg Hospital.

Parkinson's disease: biology and aetiology

The cause of dopamine cell death, thought to be the primary neurocytologic defect in idiopathic Parkinson's disease, remains unknown. Mitochondrial oxidative dysfunction causes premature cell death, and may be linked to accelerated apoptosis, excessive free and toxic radicals, deficient neurotrophic factors or combinations of these detrimental factors. Neurochemical imbalances result both in the substantia nigra and neostriatum, resulting in compensatory mechanisms that make this chronic neurodegenerative disease difficult to evaluate. Acute parkinsonism models have limitations when compared with chronic disease states, and caution should be present when comparing 'parkinsonism' data with human disease. Better understanding of classical neurotransmitters, neuroactive peptides and neurotrophic factors, will hopefully lead to more rational treatment approaches, cellular support strategies, and an understanding of the causes of this disease. Glial derived neurotrophic factor looks the most promising neurotrophic candidate so far tested in culture and in vivo. The result of clinical trials utilizing neurotrophic factors, both as mesencephalic implant support strategies and as definitive treatment of idiopathic Parkinson's disease, are awaited with cautious optimism.

Differential release of acetylcholinesterase in vivo, from the guinea pig substantia nigra compared to the caudate putamen following dopamine depletion

In the substantia nigra acetylcholinesterase may have a novel role unrelated to acetylcholine but linked instead to dopamine. Using a sensitive chemiluminescent system, we have investigated the effects of dopamine depletion on the vivo release of acetylcholinesterase in both the substantia nigra and the caudate putamen. Dopamine levels in the caudate putamen were significantly depleted compared to the non-lesioned side, using either of two different toxins for dopaminergic nigrostriatal cells: 6-hydroxydopamine ( 1 or 3 weeks prior to study) or N-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (1 week prior to study). Spontaneous release of acetylcholinesterase from the substantia nigra was significantly reduced following all three pretreatments; however, in the caudate putamen a significant reduction in the spontaneous release of acetylcholinesterase, compared to controls, was only seen in animals studied 1 week after the administration of 6-hydroxydopamine. In all control groups, application of potassium ions (60 mM) evoked a significant release of acetylcholinesterase in the substantia nigra (p < 0.05) and this effect persisted in the surviving neurones following a partial lesion by neurotoxin pre-treatment. The results from this study are discussed in the light of a regulatory mechanism for acetylcholinesterase release from the striatum, which may come into operation depending on the extent of destruction of dopaminergic nigrostriatal neurones.

Increased iron in the substantia nigra compacta of the MPTP-lesioned hemiparkinsonian African green monkey: evidence from proton microprobe elemental microanalysis

The association of free radicals and particularly free iron in the pathogenesis of idiopathic Parkinson's disease and MPTP-induced parkinsonism remains controversial. Whereas the actual cause of dopamine cell death in the substantia nigra compacta (SNc) remains unknown, disturbances in lipid peroxidation and subsequent mitochondrial and cell membrane disruption has been demonstrated. In a genetically susceptible host, abnormal elimination of oxygen and trace metal free radicals may further damage dopamine cells. Using a unilaterally MPTP-treated African Green monkey, which showed obvious contralateral hemiparkinsonism, the total free iron concentration was measured. Iron, Fe2+ and Fe3+, but not other trace elements, was significantly elevated in the SNc compared with the opposite unlesioned side, which was similar to separate control animals. Iron content in the SNc, periaqueductal gray area, and crus cerebri was 228-270 ppm. Normal control SNc was 285 (+/- 59) ppm, whereas iron levels of 532 (+/- 151) ppm were found in the MPTP-lesioned SNc. These animals were drug naive and not on long-term levodopa maintenance. Proton microprobe elemental analysis was matched against adjacent immunocytochemically stained tissue slices to ensure the cells studied were in the SNc. Iron was found not only in the degenerating dopamine cells themselves but also in the surrounding matrix and glial cells. Whether free iron that is not bound to neuromelanin is responsible for dopamine cell death as suggested by these experiments remains to be proved.

Botulinum A chemodenervation: a new modality in cerebral palsied hands

Botulinum A chemodenervation of the Adductor Pollicis muscle for the treatment of the thumb-in-palm deformity in cerebral palsied hands is presented as a new therapeutic option. Early results of a clinical trial in five hemiparetic Cerebral Palsied (C.P.) children are assessed using a prospective nontrialist-biased study design based on an independent panel assessment of pre- and post-intervention photographic and videotaped records of hand function and appearance, in combination with grip dynamometry and goniometry. All cases are shown to improve in terms of both function and appearance with results approaching statistical significance (p = 0.06) when assessed by the Wilcoxon's matched-pairs signed rank test, despite the small study group. The modality is shown to be simple, safe and effective over the period reported (229 days). The benefit is sustained beyond the period of muscle paresis and ongoing long term follow-up will document the need for, and timing of, reinjection.

Sinemet (CR4): an open-label study in moderately severe Parkinson's disease

Almost all patients with idiopathic Parkinson's disease respond to levodopa and progress steadily, requiring an increased overall dosage with time. Sinemet CR4 offers a theoretically attractive method of achieving gradual sustained release of levodopa over time which may be more physiological to striatal dopamine receptors in the early stages of the disease. This study evaluated 20 patients with moderate to severe Parkinson's disease who were treated with Sinemet CR4 over a 1-year period. Eleven patients completed the full year on therapy, and nine subjects withdrew. Of the withdrawals, two subjects died from non-Parkinson's disease-related illness, three showed no therapeutic benefit, and four responded well for a minimal 6-month period, but then lost therapeutic benefit and developed more severe dystonias. A higher overall levodopa dosage was required by all patients, and side-effects of levodopa were still present in most patients. However, the nocturnal benefit of this long-acting preparation was observed by all the patients in the study. Slow onset of action of Sinemet CR4 resulted in early-morning immobility. Sinemet CR4 cannot replace standard Sinemet, but appears to be a useful form of adjunct therapy in selected patients.

Adjunctive therapy with bromocriptine in Parkinson's disease

Patients with moderately severe Parkinson's disease complicated by the adverse effects of chronic levodopa use benefited from the addition of bromocriptine (Parlodel; Sandoz) in doses up to 26 mg daily, which allowed an approximate 30% reduction of levodopa dose. This resulted in a significant decrease in the amount of levodopa side-effects while maintaining or improving the original parkinsonian clinical stage. Increased effectiveness in these patients was not associated with increased dosage beyond 25-30 mg daily. When the doses of bromocriptine were increased slowly, the adverse reactions were minor and usually transient.

Pure word deafness

Two cases of pure word deafness, both with bilateral temporal lobe lesions due to cerebrovascular disease, are presented. This rare disorder is briefly discussed.

The antiparkinsonian activity of CQA 206-291, a new D2 dopamine receptor agonist

CQA 206-291, a new D2 dopamine receptor agonist with a biphasic dopaminergic profile, was given to six patients with idiopathic Parkinson's disease after overnight drug withdrawal. With incremental single oral doses of CQA, a dose-related, clinically significant, and prolonged antiparkinsonian effect was observed. Most subjects experienced drowsiness after the drug while a minority of subjects experienced nausea and/or vomiting or postural hypotension. Further study of this drug in humans is indicated.

A strategy for measuring the therapeutic properties of new antiparkinsonian drugs, such as +PHNO, in patients with on-off fluctuations

We describe a simple quantitative bedside method for assessing the dopaminergic properties of new therapeutic agents, namely, by documenting their duration of action in patients with Parkinson's disease who exhibit "on-off" fluctuations. This model represents a form of human dopaminergic "bioassay".

Antiparkinsonian activity of CY 208-243, a partial D-1 dopamine receptor agonist, in MPTP-treated marmosets and patients with Parkinson's disease

The effect of stimulation of cerebral dopamine D-1 receptors by CY 208-243 on motor disability was tested in MPTP-treated parkinsonian marmosets and patients with Parkinson's disease. CY 208-243 (0.5-1.25 mg/kg s.c.) produced a dose-related reversal of akinesia and rigidity in the marmosets, lasting some 2 h. Single morning doses of CY 208-243 (5-40 mg) were compared with the usual morning dose of levodopa in eight patients with Parkinson's disease on long-term levodopa therapy who had developed motor fluctuations from immobility with akinesia and rigidity (off) to mobility often with dyskinesias (on). CY 208-243 alone was capable of switching such patients from off to on; five of the eight patients responded to the highest dose (40 mg), sometimes with dyskinesias. The response to CY 208-243 was comparable to that produced by levodopa in these cases. Drugs designed to stimulate both dopamine D1 and D2 receptors in the brain may improve the therapy of Parkinson's disease.

The D-1 dopamine receptor partial agonist, CY 208-243, exhibits antiparkinsonian activity in the MPTP-treated marmoset

Administration of L-DOPA plus carbidopa, or the D-2 agonist (+)-PHNO, to MPTP-treated common marmosets caused motor hyperactivity and a reversal of the parkinsonian syndrome. In contrast, administration of the putative D-1 agonist SKF 38393 was without effect on movement or motor disability. The subsequent administration of another putative selective D-1 partial agonist CY 208-243 produced a dose-related improvement in motor activity and reversal of parkinsonian motor deficits in MPTP-treated animals. The effect of CY 208-243 was inhibited by pretreatment with the D-1 antagonist SCH 23390 and, to a lesser extent, by the D-2 antagonist sulpiride. In another group of normal drug naive marmosets, the administration of CY 208-243 produced only a small increase in motor activity. Following treatment with MPTP and without other drug administration, administration of CY 208-243 produced a marked reversal of motor deficits and locomotor hyperactivity. Thus, CY 208-243, suggested to be a partial D-1 agonist exhibits antiparkinsonian activity in MPTP-treated marmosets which does not require prior or concurrent exposure to D-2 agonists.

The value of magnetic resonance imaging in multiple sclerosis in South African-born patients

The results of magnetic resonance imaging (MRI) in supporting the diagnosis of multiple sclerosis in 24 South African-born white patients were studied. MRI confirmed the diagnosis in 87.5% of cases. It appears that MRI is useful in strengthening the diagnosis of multiple sclerosis in patients with clinically established disease. This study supports the validity of the clinical diagnosis of multiple sclerosis in South African patients and stresses the need for re-evaluation of the incidence and prevalence of multiple sclerosis in this country.