A rapidly acquired foraging-based working memory task, sensitive to hippocampal lesions, reveals age-dependent and age-independent behavioural changes in a mouse model of amyloid pathology.

Three experiments examined the ability of mice to forage efficiently for liquid rewards in pots located in an open field arena. Search behaviour was unconstrained other than by the walls of the arena. All mice acquired the task within 4 days of training, with one trial per day. Experiment 1 tested the hypothesis that hippocampal lesions would disrupt foraging behaviour using extramaze cues. Mice with hippocampal lesions showed normal latency to initiate foraging and to complete the task relative to sham-operated mice. However, lesioned mice showed increased perseverative responding (sensitization) to recently rewarded locations, increased total working memory errors and an increased propensity to search near previously rewarded locations. In Experiment 2, the extramaze cues were obscured and each pot was identified by a unique pattern. Under these conditions, mice with hippocampal lesions showed comparable working memory errors to control mice. However, lesioned mice continued to display increased perseverative responding and altered search strategies. Experiment 3 tested the hypothesis that age-related accumulation of amyloid would disrupt foraging behaviour in transgenic PDAPP mice expressing the V717F amyloid precursor protein (APP) mutation. Consistent with previous findings, PDAPP mice showed both age-dependent and age-independent behavioural changes. More specifically, 14-16 month-old PDAPP mice showed a deficit in perseverative responding and working memory errors. In contrast, changes in search behaviour, such as systematic circling, were present throughout development. The latter indicates that APP overexpression contributed to some features of the PDAPP behavioural phenotype, whereas working memory and flexible responding was sensitive to ageing and ß-amyloid burden. In conclusion, the present study provided novel insight into the role of the hippocampus and the effects of APP overexpression on memory and search behaviour in an open-field foraging task.

Route of Administration Affects Corticosteroid Sensitivity of a Combined Ovalbumin and Lipopolysaccharide Model of Asthma Exacerbation in Guinea Pigs.

Lipopolysaccharide (LPS) contributes to asthma exacerbations and development of inhaled corticosteroid insensitivity. Complete resistance to systemic corticosteroids is rare, and most patients lie on a continuum of steroid responsiveness. This study aimed to examine the sensitivity of combined ovalbumin- (Ova) and LPS-induced functional and inflammatory responses to inhaled and systemic corticosteroid in conscious guinea pigs to test the hypothesis that the route of administration affects sensitivity. Guinea pigs were sensitized to Ova and challenged with inhaled Ova alone or combined with LPS. Airway function was determined by measuring specific airway conductance via whole-body plethysmography. Airway hyper-responsiveness to histamine was determined before and 24 hours post-Ova challenge. Airway inflammation and underlying mechanisms were determined from bronchoalveolar lavage cell counts and lung tissue cytokines. Vehicle or dexamethasone was administered by once-daily i.p. injection (5, 10, or 20 mg/kg) or twice-daily inhalation (4 or 20 mg/ml) for 6 days before Ova challenge or Ova with LPS. LPS exacerbated Ova-induced responses, elongating early asthmatic responses (EAR), prolonging histamine bronchoconstriction, and further elevating airway inflammation. Intraperitoneal dexamethasone (20 mg/kg) significantly reduced the elongated EAR and airway inflammation but not the increased bronchoconstriction to histamine. In contrast, inhaled dexamethasone (20 mg/ml), which inhibited responses to Ova alone, did not significantly reduce functional and inflammatory responses to combined Ova and LPS. Combined Ova and LPS-induced functional and inflammatory responses are insensitive to inhaled, but they are only partially sensitive to systemic, dexamethasone. This finding suggests that the route of corticosteroid administration may be important in determining corticosteroid sensitivity of asthmatic responses.

Decreasing the expression of PICALM reduces endocytosis and the activity of ß-secretase: implications for Alzheimer's disease.

BACKGROUND: Polymorphisms in the gene for phosphatidylinositol binding clathrin assembly protein (PICALM), an endocytic-related protein, are associated with a small, increased risk of developing Alzheimer's disease (AD), strongly suggesting that changes in endocytosis are involved in the aetiology of the disease. We have investigated the involvement of PICALM in the processing of amyloid precursor protein (APP) to understand how PICALM could be linked to the development of AD. We used siRNA to deplete levels of PICALM, its isoforms and clathrin heavy chain in the human brain-derived H4 neuroglioma cell line that expresses endogenous levels of APP. We then used Western blotting, ELISA and immunohistochemistry to detect intra- and extracellular protein levels of endocytic-related proteins, APP and APP metabolites including ß-amyloid (Aß). Levels of functional endocytosis were quantified using ALEXA 488-conjugated transferrin and flow cytometry as a marker of clathrin-mediated endocytosis (CME). RESULTS: Following depletion of all the isoforms of PICALM by siRNA in H4 cells, levels of intracellular APP, intracellular ß-C-terminal fragment (ß-CTF) and secreted sAPPß (APP fragments produced by ß-secretase cleavage) were significantly reduced but Aß40 was not affected. Functional endocytosis was significantly reduced after both PICALM and clathrin depletion, highlighting the importance of PICALM in this process. However, depletion of clathrin did not affect APP but did reduce ß-CTF levels. PICALM depletion altered the intracellular distribution of clathrin while clathrin reduction affected the subcellular pattern of PICALM labelling. Both PICALM and clathrin depletion reduced the expression of BACE1 mRNA and PICALM siRNA reduced protein levels. Individual depletion of PICALM isoforms 1 and 2 did not affect APP levels while clathrin depletion had a differential effect on the isoforms, increasing isoform 1 while decreasing isoform 2 expression. CONCLUSIONS: The depletion of PICALM in brain-derived cells has significant effects on the processing of APP, probably by reducing CME. In particular, it affects the production of ß-CTF which is increasingly considered to be an important mediator in AD independent of Aß. Thus a decrease in PICALM expression in the brain could be beneficial to slow or prevent the development of AD.

Adherence to Parkinson's disease medication: A case study to illustrate reasons for non-adherence, implications for practice and engaging under-represented participants in research.

Parkinson's disease (PD) is a progressive neurodegenerative disease which primarily presents with the core symptoms of rigidity, postural instability, tremor, and bradykinesia. Non-adherence to prescribed PD treatments can have significant ramifications, such as poor symptom control and greater disease burden. Reasons for poor adherence are multifaceted, particularly when medication regimens are complex and often based on perceptual and practical barriers. Additionally, engaging fully non-adherent patients in research is challenging since they may have dropped out of service provision, yet their contribution is vital to fully understand the rationale for non-adherence. This paper aims to present a case study on the perspectives of one person with PD, a participant in a previously published qualitative study investigating the barriers and facilitators to medication adherence in PD. In this paper, the participant's diagnostic journey is described, and experiences of medical consultations are summarised to explain their reasons for not adhering to any of the standard UK PD treatments prescribed. The participant's preferences for using Vitamin B1 (thiamine) injections to manage the symptoms are reported and the rationale for doing so is discussed. We consider the case through the lens of a behavioural science approach, drawing on health psychology theory, the Theoretical Domains Framework (TDF), to inform the review and the practical challenges faced when analysing the data for this participant. Implications for pharmacy practice, in particular, are also put forward with view to ensuring that patients such as Mr. Wilkinson are provided with the opportunity to discuss treatment choices and self-management of long-term conditions such as PD. We also discuss the importance of reaching under-represented members of the population in medication adherence research, which embraces the principles of equality, diversity, and inclusion in research.

Upregulation of endocytic protein expression in the Alzheimer's disease male human brain.

Amyloid-beta (Aß) is produced from amyloid precursor protein (APP) primarily after APP is internalised by endocytosis and clathrin-mediated endocytic processes are altered in Alzheimer's disease (AD). There is also evidence that cholesterol and flotillin affect APP endocytosis. We hypothesised that endocytic protein expression would be altered in the brains of people with AD compared to non-diseased subjects which could be linked to increased Aß generation. We compared protein expression in frontal cortex samples from men with AD compared to age-matched, non-diseased controls. Soluble and insoluble Aß40 and Aß42, the soluble Aß42/Aß40 ratio, ßCTF, BACE1, presenilin-1 and the ratio of phosphorylated:total GSK3ß were significantly increased while the insoluble Aß42:Aß40 ratio was significantly decreased in AD brains. Total and phosphorylated tau were markedly increased in AD brains. Significant increases in clathrin, AP2, PICALM isoform 4, Rab-5 and caveolin-1 and 2 were seen in AD brains but BIN1 was decreased. However, using immunohistochemistry, caveolin-1 and 2 were decreased. The results obtained here suggest an overall increase in endocytosis in the AD brain, explaining, at least in part, the increased production of Aß during AD.

Potential Implications of Angiotensin-converting Enzyme 2 Blockades on Neuroinflammation in SARS-CoV-2 Infection.

BACKGROUND: Angiotensin-converting enzyme 2 (ACE2) has been reported as a portal for the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Consequently, scientific strategies to combat coronavirus disease of 2019 (COVID-19) were targeted to arrest SARS-CoV-2 invasion by blocking ACE2. While blocking ACE2 appears a beneficial approach to treat COVID-19, clinical concerns have been raised primarily due to the various intrinsic roles of ACE2 in neurological functions. Selective reports indicate that angiotensin receptor blockers (ARBs) and angiotensin-converting enzyme inhibitors (ACEIs) upregulate ACE2 levels. ACE2 metabolizes angiotensin II and several peptides, including apelin-13, neurotensin, kinetensin, dynorphin, (des-Arg9) bradykinin, and (Lys-des-Arg9)-bradykinin, which may elicit neuroprotective effects. Since ARBs and ACEIs upregulate ACE2, it may be hypothesized that patients with hypertension receiving ARBs and ACEIs may have higher expression of ACE2 and thus be at a greater risk of severe disease from the SARS-CoV-2 infections. However, recent clinical reports indicate the beneficial role of ARBs/ACEIs in reducing COVID-19 severity. Together, this warrants a further study of the effects of ACE2 blockades in hypertensive patients medicated with ARBs/ACEIs, and their consequential impact on neuronal health. However, the associations between their blockade and any neuroinflammation also warrant further research. OBJECTIVE: This review collates mechanistic insights into the dichotomous roles of ACE2 in SARSCoV- 2 invasion and neurometabolic functions and the possible impact of ACE2 blockade on neuroinflammation. CONCLUSION: It has been concluded that ACE2 blockade imposes neuroinflammation.

Clathrin-mediated endocytic proteins are upregulated in the cortex of the Tg2576 mouse model of Alzheimer's disease-like amyloid pathology.

Amyloid-ß (Aß) is cleaved from amyloid precursor protein (APP) predominantly after APP has trafficked through the secretory pathway and then become re-internalised by endocytosis. Clathrin-mediated and, more recently, clathrin-independent endocytosis have both been implicated in this process. Furthermore, endocytic abnormalities have been identified in cases of Alzheimer's disease (AD), however, the relevance of these changes to the aetiology of the disease remains unclear. We therefore examined the expression of proteins related to these endocytic processes in the cortex of Tg2576 mice that overexpress the Swedish mutation in APP, and consequently overexpress Aß, to determine if there were any changes in their associated pathways. We identified significant increases in the levels of clathrin, dynamin and PICALM, all proteins intimately involved with the clathrin-mediated endocytic pathway, in the transgenic animals. However, levels of proteins associated with flotillin or caveolin-mediated endocytic pathways remained unchanged. These results emphasise the importance of clathrin-mediated endocytosis in the aetiology of AD and reinforce the results of the recent GWAS studies that identified genes for clathrin-mediated endocytosis as susceptibility genes for AD. Such studies in transgenic mice will allow us to learn more about the role of clathrin-mediated endocytosis in AD.

Planning changes to health library services on the basis of impact assessment.

BACKGROUND: Various methods of impact assessment for health library services exist, including a toolkit developed for the UK. The Knowledge, Resource and Information service (KRIS) for health promotion, health service commissioning and public health (Bristol area, UK) commissioned an independent team at Aberystwyth University to provide an impact assessment and evaluation of their services and to provide evidence for future planning. OBJECTIVE: The review aimed to provide an action plan for KRIS through assessing the impact of the current service, extent of satisfaction with existing services and views on desirable improvements. METHODS: Existing impact toolkit guidance was used, with an adapted impact questionnaire, which was distributed by the KRIS staff to 244 users (response rate 62.3%) in early 2009. The independent team analysed the questionnaire data and presented the findings. RESULTS: Users valued the service (93% considered that relevant information was obtained). The most frequent impacts on work were advice to patients, clients or carers, and advice to colleagues. Literature searching and current awareness services saved staff time. Many users were seeking health promotion materials. CONCLUSION: The adapted questionnaire worked well in demonstrating the service impacts achieved by KRIS, as well as indicating desirable improvements in service delivery.

Selective reduction of APP-BACE1 activity improves memory via NMDA-NR2B receptor-mediated mechanisms in aged PDAPP mice.

ß-Amyloid (Aß) accumulation is an early event of Alzheimer's disease (AD) pathogenesis. Inhibition of Aß production by ß-secretase (BACE) has been proposed as a potential therapeutic strategy for AD. However, BACE inhibitors lack specificity and have had limited clinical benefit. To better study the consequences of reducing BACE metabolism, specifically of APP, we used an antibody, 2B3, that binds to APP at the BACE cleavage site, inhibiting Aß production. 2B3 was administered either directly into the lateral ventricles or by intraperitoneal injection to (platelet-derived growth factor promoter hAPP717V (PDAPP) mice and WT mice. 2B3 reduced soluble Aß40 and ßCTF (ß-amyloid derived C-terminal fragment) and improved memory for object-in-place associations and working memory in a foraging task in PDAPP mice. 2B3 also normalized the phosphorylation of the N-methyl-D-aspartate receptor NR2B subunit and subsequent extracellular signal-regulated kinase signaling. The importance of this NR2B pathway for OiP memory was confirmed by administering the NR2B antagonist, Ro25-6981, to 18-month-old WT. In contrast, 2B3 impaired associative recognition memory in young WT mice. These data provide novel insights into the mechanism by which selective modulation of APP metabolism by BACE influences synaptic and cognitive processes in both normal mice and aged APP transgenic mice.

Proteins Involved in Endocytosis Are Upregulated by Ageing in the Normal Human Brain: Implications for the Development of Alzheimer's Disease.

The greatest risk factor for Alzheimer's disease (AD) is advanced age, but the reason for this association remains unclear. Amyloid-ß (Aß) is produced from amyloid precursor protein (APP) primarily after APP is internalized by clathrin-mediated or clathrin-independent endocytosis. Changes in endocytosis in AD have been identified. We hypothesized that endocytic protein expression is altered during ageing, thus influencing the likelihood of developing AD by increasing Aß production. We explored how levels of endocytic proteins, APP, its metabolites, secretase enzymes, and tau varied with age in cortical brain samples from men of three age ranges (young [20-30], middle aged [45-55], and old [70-90]) with no symptoms of dementia. Aß40 and Aß42 were significantly increased in old brains, while APP and secretase expression was unaffected by age. Phosphorylated GSK3ß increased significantly with age, a possible precursor for neurofibrillary tangle production, although phosphorylated tau was undetectable. Significant increases in clathrin, dynamin-1, AP180, Rab-5, caveolin-2, and flotillin-2 were seen in old brains. Rab-5 also increased in middle-aged brains prior to changes in Aß levels. This age-related increase in endocytic protein expression, not described previously, suggests an age-related upregulation of endocytosis which could predispose older individuals to develop AD by increasing APP internalization and Aß generation.

Synthesis of the pyrrolidinone core of KSM-2690 B.

[reaction: see text] The first synthesis of the pyrrolidinone core of the polyene beta-lactone antibiotic KSM-2690 B is described. An ammonia-free Birch reductive aldol reaction utilizing acetaldehyde is one of the key steps, together with a ruthenium-catalyzed alkene isomerization reaction.

Alterations in endocytic protein expression with increasing age in the transgenic APP695 V717I London mouse model of amyloid pathology: implications for Alzheimer's disease.

A major risk factor for the development of Alzheimer's disease (AD) is increasing age, but the reason behind this association has not been identified. It is thought that the changes in endocytosis seen in AD patients are causal for this condition. Thus, we hypothesized that the increased risk of developing AD associated with ageing may be because of changes in endocytosis. We investigated using Western blotting whether the expression of endocytic proteins involved in clathrin-mediated and clathrin-independent endocytosis are altered by increasing age in a mouse model of amyloid pathology. We used mice transgenic for human amyloid precursor protein containing the V717I London mutation. We compared the London mutation mice with age-matched wild-type (WT) controls at three ages, 3, 9 and 18 months, representing different stages in the development of pathology in this model. Having verified that the London mutation mice overexpressed amyloid precursor protein and ß-amyloid, we found that the expression of the smallest isoform of PICALM, a key protein involved in the regulation of clathrin-coated pit formation, was significantly increased in WT mice, but decreased in the London mutation mice with age. PICALM levels in WT 18-month mice and clathrin levels in WT 9-month mice were significantly higher than those in the London mutation mice of the same ages. The expression of caveolin-1, involved in clathrin-independent endocytosis, was significantly increased with age in all mice. Our results suggest that endocytic processes could be altered by the ageing process and such changes could partly explain the association between ageing and AD.

An antibody to the beta-secretase cleavage site on amyloid-beta-protein precursor inhibits amyloid-beta production.

Proteolytic cleavage of amyloid-beta-protein precursor (AbetaPP) by beta- and gamma-secretases results in production of the amyloid-beta peptide (Abeta) that accumulates in the brains of sufferers of Alzheimer's disease (AD). We have developed a monoclonal antibody, 2B12, which binds in the vicinity of the beta-secretase cleavage site on AbetaPP but does not bind within the Abeta region. We hypothesised that this antibody, directed against the substrate rather than the enzyme, could inhibit cleavage of AbetaPP by beta-secretase via steric hindrance and thus reduce downstream production of Abeta. The antibody would enter cells by binding to AbetaPP when it is at the cell surface and then be internalised with the protein. We subsequently demonstrated that, after addition of 2B12 to standard growth media, this antibody was indeed capable of inhibiting Abeta40 production in neuroblastoma and astrocytoma cells expressing native AbetaPP, as measured by an ELISA. This inhibition was both concentration- and time-dependent and was specific to 2B12. We were only able to inhibit approximately 50% of Abeta40 production suggesting that not all AbetaPP is trafficked to the cell surface. We propose that this antibody could be used as a novel, putative therapy for the treatment of AD.

Diel Surface Temperature Range Scales with Lake Size.

Ecological and biogeochemical processes in lakes are strongly dependent upon water temperature. Long-term surface warming of many lakes is unequivocal, but little is known about the comparative magnitude of temperature variation at diel timescales, due to a lack of appropriately resolved data. Here we quantify the pattern and magnitude of diel temperature variability of surface waters using high-frequency data from 100 lakes. We show that the near-surface diel temperature range can be substantial in summer relative to long-term change and, for lakes smaller than 3 km2, increases sharply and predictably with decreasing lake area. Most small lakes included in this study experience average summer diel ranges in their near-surface temperatures of between 4 and 7°C. Large diel temperature fluctuations in the majority of lakes undoubtedly influence their structure, function and role in biogeochemical cycles, but the full implications remain largely unexplored.

Identification of novel alternative splicing events in the huntingtin gene and assessment of the functional consequences using structural protein homology modelling.

Huntington's disease (HD) is an inherited progressive neurodegenerative disorder caused by a pathological CAG trinucleotide repeat expansion in the large multi-exon gene, huntingtin (HTT). Although multiple pathogenic mechanisms have been proposed for HD, there is increasing interest in the RNA processing of the HTT gene. In mammals, most multi-exon genes are alternatively spliced; however, few alternative transcripts have been described for HTT. Given the numerous protein bands detected in mouse and human brain tissue by Western blotting using anti-huntingtin antibodies, we examined whether alternative splicing of HTT may account for some of these fragments. Using RT-PCR in mouse brain, we detected two novel splice variants of Htt that lacked the 111-bp exon 29 (Htt∆ex29) or retained a 57-bp portion of intron 28 (Htt(+57)in28) via use of a cryptic splice site. The alternative transcripts were present in wild-type and homozygous Hdh(Q150/Q150) mouse brain at all ages and in all brain regions and peripheral tissues studied. Differential splicing of Htt∆ex29 was found in the cerebellum of Hdh(Q150/Q150) mice with a significant reduction in transcript levels in mutant animals. In human brain, we detected similar splice variants lacking exons 28 and 29. The ability of alternatively spliced transcripts to encode different protein isoforms with individual functions in the cell, combined with the known role of splicing in disease, renders these novel transcripts of interest in the context of HD pathogenesis.

Inhibition of amyloid-ß production by anti-amyloid precursor protein antibodies in primary mouse cortical neurones.

Current therapies for Alzheimer's disease only treat the symptoms of the disease. We have previously developed a novel monoclonal antibody, 2B3, which binds to the ß-secretase cleavage site in amyloid precursor protein (APP) and reduces the production of amyloid-ß (Aß) in human cell lines. To determine whether the antibody was likely to be effective in mouse models of amyloid pathology in vivo, we investigated whether 2B3 could also bind to APP in mouse primary cortical neurones. Primary cortical neurones were produced from E15.5-17.5 C57Bl/6 wild-type and transgenic APP/V717I (London mutation) embryos. The percentage of the neuronal population was determined by immunocytochemistry. Cells were treated with 10 µg/ml 2B3 or an irrelevant IgG for 48 h and Aß40 levels determined by ELISA. The population of cells was found to contain over 75% neurones and 2B3 bound effectively to these cells. No differences in Aß40 were detected between wild-type and transgenic cells. Importantly, 2B3 significantly inhibited the production of Aß40 by 75.15±1.37% of the media control, whereas an irrelevant IgG only significantly reduced Aß40 levels by 23.35±5.55% of the media control. The reduction in Aß40 produced by 2B3 was significantly greater than that caused by the IgG. These data indicate that 2B3 binds to APP in mouse neurones and can inhibit Aß40, similar to our previous findings. The antibody is probably therefore acting by steric hindrance of ß-secretase and these data suggest that it will be effective in mice in vivo and could be an alternative potential therapy for Alzheimer's disease.

Anti-amyloid precursor protein immunoglobulins inhibit amyloid-ß production by steric hindrance.

The cleavage of amyloid precursor protein (APP) by ß- and γ-secretases results in the production of amyloid-ß (Aß) in Alzheimer's disease. We raised two monoclonal antibodies, 2B3 and 2B12, that recognize the ß-secretase cleavage site on APP but not Aß. We hypothesized that these antibodies would reduce Aß levels via steric hindrance of ß-secretase. Both antibodies decreased extracellular Aß levels from astrocytoma cells, but 2B3 was more potent than 2B12. Levels of soluble sAPPα from the nonamyloidogenic α-secretase pathway and intracellular APP were not affected by either antibody nor were there any effects on cell viability. 2B3 exhibited a higher affinity for APP than 2B12 and its epitope appeared to span the cleavage site, whereas 2B12 bound slightly upstream. Both of these factors probably contribute to its greater effect on Aß levels. After 60 min incubation at pH 4.0, most 2B3 and 2B12 remained bound to their antigen, suggesting that the antibodies will remain bound to APP in the acidic endosomes where ß-secretase cleavage probably occurs. Only 2B3 and 2B12, but not control antibodies, inhibited the cleavage of sAPPα by ß-secretase in a cell-free assay where the effects of antibody internalization and intracellular degradation were excluded. 2B3 virtually abolished this cleavage. In addition, levels of C-terminal APP fragments, generated following ß-secretase cleavage (ßCTF), were significantly reduced in cells after incubation with 2B3. These results strongly suggest that anti-cleavage site IgGs can generically reduce Aß levels via inhibition of ß-secretase by steric hindrance and may provide a novel alternative therapy for Alzheimer's disease.

A new operative technique for a rare case of pyelic fusion.

This case report presents the first documented case of pyelic fusion with two sites of obstruction. The patient was diagnosed following antenatal presentation and the operative technique described in this case report is the only way by which the obstructions could be treated with a single procedure. The left pelvicalyceal system was grossly dilated and was draining into the common pelvis via an obstructed calyx in the isthmus of the horse shoe. The common ureter also had a pelviureteric junction stenosis. Incisions were made in the left dilated pelvis and in the obstructed part of the pelviureteric junction and ureter. The two openings were sutured as a culp pyeloplasty using interrupted 6/0 PDS sutures over a 4F JJ stent.

Outcome-specific satiety reveals a deficit in context-outcome, but not stimulus- or action-outcome, associations in aged Tg2576 mice.

The onset of Alzheimer's disease (AD) is often accompanied by changes in emotion, motivation, and goal-directed behavior. The production of beta-amyloid is thought to be a major and early contributor to the pathogenesis of AD. The present study tested the hypothesis that amyloid pathology present in the amygdala, frontal cortex, and hippocampus of Tg2576 mice would disrupt the development of instrumental- and/or Pavlovian-outcome associations. The results showed that both instrumental- and Pavlovian-conditioned behaviors were sensitive to outcome devaluation (Experiments 1 & 2) and that Pavlovian cues influenced goal-directed actions associated with the same outcome (Experiment 2) in Tg2576 mice. In contrast, context mediated Pavlovian-conditioned behaviors in aged (Experiment 3a) but not young (Experiment 3b) Tg2576 mice were insensitive to outcome devaluation. Aged Tg2576, nevertheless, successfully acquired a simple context discrimination at the same rate as control mice. We conclude that amyloid pathology in aged Tg2576 mice may specifically disrupt context-outcome associations supported by the hippocampus and/or its interaction with the amygdala.

Effects of Wnt3A and mechanical load on cartilage chondrocyte homeostasis.

INTRODUCTION: Articular cartilage functions in withstanding mechanical loads and provides a lubricating surface for frictionless movement of joints. Osteoarthritis, characterised by cartilage degeneration, develops due to the progressive erosion of structural integrity and eventual loss of functional performance. Osteoarthritis is a multi-factorial disorder; two important risk factors are abnormal mechanical load and genetic predisposition. A single nucleotide polymorphism analysis demonstrated an association of hip osteoarthritis with an Arg324Gly substitution mutation in FrzB, a Wnt antagonist. The purpose of this study was two-fold: to assess whether mechanical stimulation modulates ß-catenin signalling and catabolic gene expression in articular chondrocytes, and further to investigate whether there is an interplay of mechanical load and Wnt signalling in mediating a catabolic response. METHODS: Chondrocytes were pre-stimulated with recombinant Wnt3A for 24 hours prior to the application of tensile strain (7.5%, 1 Hz) for 30 minutes. Activation of Wnt signalling, via ß-catenin nuclear translocation and downstream effects including the transcriptional activation of c-jun, c-fos and Lef1, markers of chondrocyte phenotype (type II collagen (col2a1), aggrecan (acan), SOX9) and catabolic genes (MMP3, MMP13, ADAMTS-4, ADAMTS-5) were assessed. RESULTS: Physiological tensile strain induced col2a1, acan and SOX9 transcription. Load-induced acan and SOX9 expression were repressed in the presence of Wnt3A. Load induced partial ß-catenin nuclear translocation; there was an additive effect of load and Wnt3A on ß-catenin distribution, with both extensive localisation in the nucleus and cytoplasm. Immediate early response (c-jun) and catabolic genes (MMP3, ADAMTS-4) were up-regulated in Wnt3A stimulated chondrocytes. With load and Wnt3A there was an additive up-regulation of c-fos, MMP3 and ADAMTS-4 transcription, whereas there was a synergistic interplay on c-jun, Lef1 and ADAMTS-5 transcription. CONCLUSION: Our data suggest that load and Wnt, in combination, can repress transcription of chondrocyte matrix genes, whilst enhancing expression of catabolic mediators. Future studies will investigate the respective roles of abnormal loading and genetic predisposition in mediating cartilage degeneration.