Effects of chronic drug treatments on increases in intracellular calcium mediated by nicotinic acetylcholine receptors in SH-SY5Y cells

1. SH-SY5Y cells express alpha7 and alpha3* subtypes of nicotinic acetylcholine receptors (AChR). Numbers of these receptors are upregulated by chronic treatment with nicotinic agonists or KCl. In this study we have examined the functional consequences of these drug treatments on nicotine- or KCl-evoked increases in [Ca(2+)](i), in SH-SY5Y cells. 2. In untreated cells, nicotine increased [Ca(2+)](i) (EC(50) 7.5 microM). Responses to 10 microM nicotine were abolished by the non-selective nicotinic antagonist mecamylamine and were partially blocked by alpha7-selective antagonists, the alpha3beta2*-selective antagonist alpha-conotoxin-MII, and by cadmium and verapamil. 3. After treatment for 4 days with nicotinic agonists, nicotine-evoked increases in [Ca(2+)](i) were significantly decreased by about 25%. Nicotine-evoked responses were paradoxically increased in the presence of acute methyllycaconitine (MLA; an alpha7-selective antagonist) although other alpha7-selective antagonists were without effect, while alpha-conotoxin-MII gave a partial inhibition. The increase observed with MLA was abolished by mecamylamine but not by alpha-conotoxin-MII and was still observed 24 h after chronic nicotine treatment. 4. After treatment for 4 days with KCl, nicotine-evoked increases in [Ca(2+)](i) were also decreased by 25%, but acute MLA was without effect. Responses to 20 mM KCl were unchanged by prior treatment with nicotine or KCl. Treatment for 4 days with 5 microM verapamil reduced responses to both nicotine and KCl by about 50%. 5. Multiple nicotinic AChR subtypes contribute to nicotine-evoked increases in [Ca(2+)](i) in SH-SY5Y cells. Responses to acute nicotine are reduced after chronic nicotine or KCl treatment, with loss of the component attributed to the alpha7 subtype. However, in nicotine-treated cells this effect is reversed when nicotine stimulation is applied in the presence of acute MLA. The antagonist may assist in converting a non-functional alpha7 nicotinic AChR to a conducting state.     

Recombinant adeno-associated viral vector (rAAV) delivery of GDNF provides protection against 6-OHDA lesion in the common marmoset monkey (Callithrix jacchus)

Glial cell line-derived neurotrophic factor (GDNF) has shown potential as a treatment for Parkinson's disease. Recombinant adeno-associated viral vectors expressing the GDNF protein (rAAV-GDNF) have been used in rodent models of Parkinson's disease to promote functional regeneration after 6-OHDA lesions of the nigrostriatal system. The goal of the present study was to assess the anatomical and functional efficacy of rAAV-GDNF in the common marmoset monkey (Callithrix jacchus). rAAV-GDNF was injected into the striatum and substantia nigra 4 weeks prior to a unilateral 6-OHDA lesion of the nigrostriatal bundle. Forty percent of the dopamine cells in the lesioned substantia nigra of the rAAV-GDNF-treated monkeys survived, compared with 21% in the untreated monkeys. Fine dopaminergic fibres were observed microscopically in the injected striatum of some rAAV-GDNF-treated monkeys, suggesting that rAAV-GDNF treatment may have prevented, at least in part, the loss of dopaminergic innervation of the striatum. Protection of dopamine cells and striatal fibre innervation was associated with amelioration of the lesion-induced behavioural deficits. rAAV-GDNF-treated monkeys showed partial or complete protection not only in the amphetamine and apomorphine rotation but also in head position and the parkinsonian disability rating scale. Therefore, our study provides evidence for the behavioural and anatomical efficacy of GDNF delivered via an rAAV vector as a possible treatment for Parkinson's disease.     

A near fatal case of the dapsone hypersensitivity syndrome in a patient with urticarial vasculitis

Dapsone (4,4'-diaminodiphenyl sulphone) is used for a variety of dermatological conditions including immunobullous diseases and urticarial vasculitis. Side-effects are common and include lethargy, headaches, methaemoglobinaemia and haemolysis. Severe adverse effects are rare but the dapsone hypersensitivity syndrome is well recognized. Symptoms include fever, haemolytic anaemia, lymphocytosis and hepatitis. We report a near fatal case of the dapsone hypersensitivity syndrome in a patient with urticarial vasculitis. This diagnosis should be remembered in any patient who becomes unwell whilst taking dapsone.     

Uncertainty and scoring systems

Estimating risks for individual patients facilitates communication with patients, relatives and colleagues, and determines whether further treatment is futile. The process of estimating risks involves mathematics (i.e. scoring systems) and human experience and expertise. Understanding how risks are estimated is important because prognostication is an integral part of any medical specialty. In the USA, such treatment limitation or withdrawal decisions were made on only 7% of all intensive care unit patients but this represented 47% of all deaths on such units. In the UK, data reported by the Intensive Care National Audit and Research Centre suggest that although treatment limitation decisions are made on only 11.8% of patients, this accounts for over 50% of deaths on intensive care. Scoring systems offer a useful adjunct in identifying futility but there are important inherent weaknesses that limit their performance. This review aims to discuss some of these limitations.     

Assessing critical care unit performance: a global measure using graphical analysis

Outcome measurement in critical care is difficult because of the wide variety of patients treated and the diverse therapeutic options and pathways available. Individual outcome measures for critical care are available but are naturally limited to only a single aspect of performance. Most importantly, better performance in one aspect of care may compromise the standard of care in another. A global measure of performance would be helpful. For the year 1999-2000, the five hospitals in the East Anglian Critical Care Network provided data on capacity, workload and performance. The data was transformed and displayed graphically on a radar chart so that the area of the polygon within the radar chart was proportional to each unit's overall performance. The results from the five hospitals suggest that there is little overall difference in the units' global performance but the graphical representation highlighted some individual deficiencies. Graphical analysis of complex processes such as critical care delivery may facilitate performance assessment, providing that the measures chosen, weightings assigned and scales used are standardised with care.     

Normal aging and executive functions in "old-old" community dwellers: poor performance is not an inevitable outcome

BACKGROUND: Studies on normal aging and cognitive functioning commonly describe early and more pronounced age-related changes in executive functions (EFs) compared to other cognitive abilities. Two of the three most common neurodegenerative disorders associated with aging (vascular dementia [VaD] and extrapyramidal [EP]-related dementia) show executive dysfunctions in their clinical presentation; and these cognitive deficits are not uncommon in the third one: Alzheimer's disease (AD). METHODS: Nine EF tests (yielding 12 measures) were administered to 123 randomly selected community dwellers, aged 81 years and over, with the view to determine the effect of age on performance. Markers of AD, VaD, and EP-related dementia, as well as sociodemographic and psychological variables, were selected and their contribution to EF performance was investigated. RESULTS: Multiple linear regression analyses revealed the greatest contribution to EF scores from the markers of AD and estimated IQ but not from the markers of VaD and EP-related dementia or from age. CONCLUSIONS: These findings suggest that chronological age acts as a proxy variable mediating the impact of other factors such as subclinical signs of neurodegenerative disorders and that it has little independent contribution to make. They also indicate the importance of cognitive abilities supported by posterior cortical circuits in EF problem resolution. This study demonstrates that cognitive decline is not an ineluctable process that is associated with "normal" aging but rather represents, in many cases, a byproduct of neurodegenerative disorders, albeit themselves highly age-related.     

Unilateral lesions of the cholinergic basal forebrain and fornix in one hemisphere and inferior temporal cortex in the opposite hemisphere produce severe learning impairments in rhesus monkeys

It has been proposed that isolation of the inferior temporal cortex and medial temporal lobe from their cholinergic afferents results in a severe anterograde amnesia. To test this hypothesis directly, seven rhesus monkeys received a unilateral immunotoxic lesion of the cholinergic cells of the basal forebrain with an ipsilesional section of the fornix. In a second surgery, inferior temporal cortex was ablated in the opposite hemisphere. All animals were severely impaired at learning visual scenes and object-reward associations. The impairment in learning scenes was correlated with cholinergic cell loss in the basal forebrain, but not with generalized tissue damage. Two monkeys served as surgical controls with saline injection in place of the immunotoxin, but all other procedures the same, and were not as severely impaired as those with immunotoxic lesions. Previous work has shown that monkeys with bilateral section of the anterior temporal stem (white matter of the temporal lobe), amygdala and fornix show a severe new learning impairment, and provide a model of human medial temporal lobe amnesia. One effect of this combined ablation is to isolate inferior temporal cortex and medial temporal lobe from their cholinergic afferents, possibly in addition to a direct disruption of the hippocampal system. The results of the present study, then, provide a novel link between the mechanisms of medial temporal lobe amnesia and Alzheimer's disease in which the cholinergic basal forebrain shows pathology. We propose that in both cases the mnemonic impairments result from isolating inferior temporal cortex and medial temporal lobe from their cholinergic afferents, possibly in addition to a direct disruption of the hippocampal system.     

Breast cancer risk associated with different HRT formulations: a register-based case-control study

Background  

Previous epidemiological studies have inconsistently shown a modestly increased breast cancer risk associated with hormone replacement therapy (HRT). Limited information is available about different formulations - particularly concerning different progestins.     

Visual discrimination learning impairments produced by combined transections of the anterior temporal stem, amygdala and fornix in marmoset monkeys

Marmoset monkeys (Callithrix jacchus) with bilateral transections of the anterior temporal stem, amygdala and fornix were unable to relearn a 2-choice object discrimination first learnt prior to surgery, and were very severely impaired at relearning a concurrent object discrimination task which they had learnt and relearnt prior to surgery, indicating that they had a dense retrograde amnesia. They also had difficulty learning new visual object discriminations but were only mildly impaired on spatial learning. When tested on new learning of concurrent discriminations 8 to 10 weeks after surgery, three operated monkeys were unable to reach criterion in 400 trials while the remaining two operated monkeys performed within the normal range. The operated monkeys were subsequently shown to be impaired on acquisition of shape discriminations using black objects. These anterograde effects suggest that the impairment runs mainly in the domain of visual analysis. The monkeys also exhibited many of the features of the Klüver-Bucy syndrome. Histological analysis indicated that in addition to cutting some of the subcortical temporal lobe efferent pathways, the surgical procedures had cut the cholinergic afferents to the temporal neocortex, entorhinal cortex, and hippocampus. In a second experiment we found that treatment with the cholinergic agonist pilocarpine, which is effective in monkeys with specific cholinergic lesions, was unable to remediate the lesion-induced impairments. This suggests that transection of the non-cholinergic afferents, or the temporal lobe subcortical efferents, contributed to the behavioural syndrome and the learning and retention deficits seen in these monkeys.