John O'Brien

University College London, London, ENG, United Kingdom

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Publications (14)98.03 Total impact

  • Article: Stapling of the botulinum type A protease to growth factors and neuropeptides allows selective targeting of neuroendocrine cells.
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    ABSTRACT: Precise cellular targeting of macromolecular cargos has important biotechnological and medical implications. Using a recently established 'protein stapling' method, we linked the proteolytic domain of botulinum neurotoxin type A (BoNT/A) to a selection of ligands to target neuroendocrine tumor cells. The botulinum proteolytic domain was chosen due to its well-known potency to block the release of neurotransmitters and hormones. Among nine tested stapled ligands, the epidermal growth factor, EGF, was able to deliver the botulinum enzyme into pheochromocytoma PC12 and insulinoma Min6 cells; ciliary neurotrophic factor, CNTF, was effective on neuroblastoma SH-SY5Y and Neuro2A cells, whereas corticotropin-releasing hormone, CRH, was active on pituitary AtT-20 cells and the two neuroblastoma cell lines. In neuronal cultures, the EGF- and CNTF-directed botulinum enzyme targeted distinct subsets of neurons whereas the whole native neurotoxin targeted the cortical neurons indiscriminately. At nanomolar concentrations, the retargeted botulinum molecules were able to inhibit stimulated release of hormones from tested cell lines suggesting their application for treatments of neuroendocrine disorders. This article is protected by copyright. All rights reserved.
    Journal of Neurochemistry 05/2013; · 4.06 Impact Factor
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    Article: Study of E/Z Isomerization in a Series of Novel Non-ligand Binding Pocket Androgen Receptor Antagonists.
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    ABSTRACT: We report the conformational analysis of a series of 3-hydroxy-N'-((naphthalen-2-yl)methylene)naphthalene-2-carbohydrazides. This class of compounds has recently been reported as androgen receptor (AR)-coactivator disruptors for potential application in prostate cancer therapy. Definition of the E/Z isomerism around the imine linker group (hydrazide) is significant from a mechanistic point of view. A detailed study using theoretical calculations coupled with experimental techniques has allowed us determine an initial preference for the E isomer. The biological activity of newly synthesized compounds at the androgen receptor, along with a series of structural analogs, was determined and provides the basis for preliminary qualitative structure-activity relationship analysis.
    Journal of Chemical Information and Modeling 08/2012; 52(9):2387-97. · 4.68 Impact Factor
  • Article: 'Smoking' mephedrone: The identification of the pyrolysis products of 4-methylmethcathinone hydrochloride.
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    ABSTRACT: The ring-substituted cathinone - mephedrone - has gained popularity among recreational drug users over the past several years. It is generally consumed orally or by snorting but reports indicate that it is also ingested by vaporization/inhalation. This study examines the pyrolysis products produced by heating mephedrone under using simulated 'meth pipe' conditions. Thirteen pyrolysis products were identified, the major ones being iso-mephedrone, 4-methylpropiophenone, 4-methylphenylacetone, two pyrazine derivatives formed by dimerization of mephedrone, N-methylated mephedrone (N,N,4-trimethylcatinone), two hydroxylated oxidation products and a diketone. Other minor products formed were identified as 4-methylacetophenone, two α-chloro ketones and N-methylated iso-mephedrone. Copyright © 2012 John Wiley & Sons, Ltd.
    Drug Testing and Analysis 05/2012; · 2.54 Impact Factor
  • Article: Authors' reply:.
    The British journal of psychiatry: the journal of mental science 04/2012; 200:345-6. · 6.62 Impact Factor
  • Article: Donepezil and memantine for moderate-to-severe Alzheimer's disease.
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    ABSTRACT: Clinical trials have shown the benefits of cholinesterase inhibitors for the treatment of mild-to-moderate Alzheimer's disease. It is not known whether treatment benefits continue after the progression to moderate-to-severe disease. We assigned 295 community-dwelling patients who had been treated with donepezil for at least 3 months and who had moderate or severe Alzheimer's disease (a score of 5 to 13 on the Standardized Mini-Mental State Examination [SMMSE, on which scores range from 0 to 30, with higher scores indicating better cognitive function]) to continue donepezil, discontinue donepezil, discontinue donepezil and start memantine, or continue donepezil and start memantine. Patients received the study treatment for 52 weeks. The coprimary outcomes were scores on the SMMSE and on the Bristol Activities of Daily Living Scale (BADLS, on which scores range from 0 to 60, with higher scores indicating greater impairment). The minimum clinically important differences were 1.4 points on the SMMSE and 3.5 points on the BADLS. Patients assigned to continue donepezil, as compared with those assigned to discontinue donepezil, had a score on the SMMSE that was higher by an average of 1.9 points (95% confidence interval [CI], 1.3 to 2.5) and a score on the BADLS that was lower (indicating less impairment) by 3.0 points (95% CI, 1.8 to 4.3) (P<0.001 for both comparisons). Patients assigned to receive memantine, as compared with those assigned to receive memantine placebo, had a score on the SMMSE that was an average of 1.2 points higher (95% CI, 0.6 to 1.8; P<0.001) and a score on the BADLS that was 1.5 points lower (95% CI, 0.3 to 2.8; P=0.02). The efficacy of donepezil and of memantine did not differ significantly in the presence or absence of the other. There were no significant benefits of the combination of donepezil and memantine over donepezil alone. In patients with moderate or severe Alzheimer's disease, continued treatment with donepezil was associated with cognitive benefits that exceeded the minimum clinically important difference and with significant functional benefits over the course of 12 months. (Funded by the U.K. Medical Research Council and the U.K. Alzheimer's Society; Current Controlled Trials number, ISRCTN49545035.).
    New England Journal of Medicine 03/2012; 366(10):893-903. · 53.30 Impact Factor
  • Article: Atheromatous disease in small intracerebral vessels, microinfarcts and dementia.
    Neuropathology and Applied Neurobiology 02/2012; 38(5):505-8. · 3.80 Impact Factor
  • Article: The synthesis and characterization N-methyl-3-phenyl-norbornan-2-amine (Camfetamine™).
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    ABSTRACT: N-Methyl-3-phenyl-norbornan-2-amine (N-methyl-3-phenylbicyclo[2.2.1]heptan-2-amine, Camfetamine(™) ) is available from a number of online legal highs/research chemicals' vendors. Although it was developed as an analeptic by Merck in the early 1960s, it was never commercialized. However, the Association of Independent Research Chemical Retailers (AIRCR), an umbrella organization for a number of online vendors, has redeveloped it for use as a recreational drug. N-Methyl-3-phenyl-norbornan-2-amine is closely related to fencamfamine which has been widely used as a central nervous system (CNS) stimulant and appetite suppressant. In this paper we describe the synthesis of N-methyl-3-phenyl-norbornan-2-amine, its characterization and interpretations of its electron impact, and electrospray ionization mass spectra. Copyright © 2012 John Wiley & Sons, Ltd.
    Drug Testing and Analysis 02/2012; · 2.54 Impact Factor
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    Article: Assembly of protein building blocks using a short synthetic peptide.
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    ABSTRACT: Combining proteins or their defined domains offers new enhanced functions. Conventionally, two proteins are either fused into a single polypeptide chain by recombinant means or chemically cross-linked. However, these strategies can have drawbacks such as poor expression (recombinant fusions) or aggregation and inactivation (chemical cross-linking), especially in the case of large multifunctional proteins. We developed a new linking method which allows site-oriented, noncovalent, yet irreversible stapling of modified proteins at neutral pH and ambient temperature. This method is based on two distinct polypeptide linkers which self-assemble in the presence of a specific peptide staple allowing on-demand and irreversible combination of protein domains. Here we show that linkers can either be expressed or be chemically conjugated to proteins of interest, depending on the source of the proteins. We also show that the peptide staple can be shortened to 24 amino acids still permitting an irreversible combination of functional proteins. The versatility of this modular technique is demonstrated by stapling a variety of proteins either in solution or to surfaces.
    Bioconjugate Chemistry 02/2012; 23(3):479-84. · 4.93 Impact Factor
  • Article: Neuroimaging of dementia with Lewy bodies.
    John-Paul Taylor, John O'Brien
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    ABSTRACT: Dementia with Lewy bodies (DLB) is a relative newcomer to the field of late-life dementia. Although a diversity of imaging methodologies is now available for the study of dementia, these have been applied most often to Alzheimer's disease (AD). Studies on DLB, although fewer, have yielded fascinating and important insights into the underlying pathophysiology of this condition and allowed clinical differentiation of DLB from other dementias. Imaging research on DLB has had significant ramifications in terms of raising the profile of DLB and helping define it as a distinctive and separate disease entity from AD.
    Neuroimaging Clinics of North America 02/2012; 22(1):67-81, viii. · 1.51 Impact Factor
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    Article: Comparison of cognitive decline between dementia with Lewy bodies and Alzheimer's disease: a cohort study.
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    ABSTRACT: Dementia with Lewy bodies (DLB) accounts for 10%-15% of dementia cases at autopsy and has distinct clinical features associated with earlier institutionalisation and a higher level of carer distress than are seen in Alzheimer's disease (AD). At present, there is on-going debate as to whether DLB is associated with a more rapid cognitive decline than AD. An understanding of the rate of decline of cognitive and non-cognitive symptoms in DLB may help patients and carers to plan for the future. In this cohort study, the authors compared 100 AD and 58 DLB subjects at baseline and at 12-month follow-up on cognitive and neuropsychiatric measures. Patients were recruited from 40 European centres. Subjects with mild-moderate dementia. Diagnosis of DLB or AD required agreement between consensus panel clinical diagnosis and visual rating of 123I-FP-CIT (dopamine transporter) single photon emission computed tomography neuroimaging. The Cambridge Cognitive Examination including Mini-Mental State Examination and Neuropsychiatric Inventory (NPI). The AD and DLB groups did not differ at baseline in terms of age, gender, Clinical Dementia Rating score and use of cholinesterase inhibitors or memantine. NPI and NPI carer distress scores were statistically significantly higher for DLB subjects at baseline and at follow-up, and there were no differences between AD and DLB in cognitive scores at baseline or at follow-up. There was no significant difference in rate of progression of any of the variables analysed. DLB subjects had more neuropsychiatric features at baseline and at follow-up than AD, but the authors did not find any statistically significant difference in rate of progression between the mild-moderate AD and DLB groups on cognitive or neuropsychiatric measures over a 12-month follow-up period.
    BMJ open. 01/2012; 2:e000380.
  • Article: Dietary factors and low-grade inflammation in relation to overweight and obesity.
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    ABSTRACT: Low-grade inflammation is a characteristic of the obese state, and adipose tissue releases many inflammatory mediators. The source of these mediators within adipose tissue is not clear, but infiltrating macrophages seem to be especially important, although adipocytes themselves play a role. Obese people have higher circulating concentrations of many inflammatory markers than lean people do, and these are believed to play a role in causing insulin resistance and other metabolic disturbances. Blood concentrations of inflammatory markers are lowered following weight loss. In the hours following the consumption of a meal, there is an elevation in the concentrations of inflammatory mediators in the bloodstream, which is exaggerated in obese subjects and in type 2 diabetics. Both high-glucose and high-fat meals may induce postprandial inflammation, and this is exaggerated by a high meal content of advanced glycation end products (AGE) and partly ablated by inclusion of certain antioxidants or antioxidant-containing foods within the meal. Healthy eating patterns are associated with lower circulating concentrations of inflammatory markers. Among the components of a healthy diet, whole grains, vegetables and fruits, and fish are all associated with lower inflammation. AGE are associated with enhanced oxidative stress and inflammation. SFA and trans-MUFA are pro-inflammatory, while PUFA, especially long-chain n-3 PUFA, are anti-inflammatory. Hyperglycaemia induces both postprandial and chronic low-grade inflammation. Vitamin C, vitamin E and carotenoids decrease the circulating concentrations of inflammatory markers. Potential mechanisms are described and research gaps, which limit our understanding of the interaction between diet and postprandial and chronic low-grade inflammation, are identified.
    The British journal of nutrition 12/2011; 106 Suppl 3:S5-78. · 3.45 Impact Factor
  • Article: Dietary factors and low-grade inflammation in relation to overweight and obesity
    [show abstract] [hide abstract]
    ABSTRACT: Low-grade inflammation is a characteristic of the obese state, and adipose tissue releases many inflammatory mediators. The source of these mediators within adipose tissue is not clear, but infiltrating macrophages seem to be especially important, although adipocytes themselves play a role. Obese people have higher circulating concentrations of many inflammatory markers than lean people do, and these are believed to play a role in causing insulin resistance and other metabolic disturbances. Blood concentrations of inflammatory markers are lowered following weight loss. In the hours following the consumption of a meal, there is an elevation in the concentrations of inflammatory mediators in the bloodstream, which is exaggerated in obese subjects and in type 2 diabetics. Both high-glucose and high-fat meals may induce postprandial inflammation, and this is exaggerated by a high meal content of advanced glycation end products (AGE) and partly ablated by inclusion of certain antioxidants or antioxidant-containing foods within the meal. Healthy eating patterns are associated with lower circulating concentrations of inflammatory markers. Among the components of a healthy diet, whole grains, vegetables and fruits, and fish are all associated with lower inflammation. AGE are associated with enhanced oxidative stress and inflammation. SFA and trans-MUFA are pro-inflammatory, while PUFA, especially long-chain n-3 PUFA, are anti-inflammatory. Hyperglycaemia induces both postprandial and chronic low-grade inflammation. Vitamin C, vitamin E and carotenoids decrease the circulating concentrations of inflammatory markers. Potential mechanisms are described and research gaps, which limit our understanding of the interaction between diet and postprandial and chronic low-grade inflammation, are identified.
    The British journal of nutrition 11/2011; 106. · 3.45 Impact Factor
  • Article: Pyridin-2-yl guanidine derivatives: conformational control induced by intramolecular hydrogen-bonding interactions.
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    ABSTRACT: The synthesis and conformational analysis of a series of pyridin-2-yl guanidine derivatives using NMR, X-ray crystallography, and B3LYP/6-31+G** theoretical studies are reported. A remarkable difference was observed in the (1)H NMR spectra of the guanidinium salts as compared with their N,N'-di-Boc protected and neutral analogues. This difference corresponds to a 180° change in the dihedral angle between the guanidine/ium moiety and the pyridine ring in the salts as compared to the Boc-protected derivatives, a conclusion that was supported by theoretical studies, X-ray data, and NMR analysis. Moreover, our data sustain the existence of two intramolecular hydrogen-bonding systems: (i) between the pyridine N1 atom and the guanidinium protons in the salts and (ii) within the tert-butyl carbamate groups of the Boc-protected derivatives. To verify that the observed conformational control arises from these intramolecular interactions, a new series of N-Boc-N'-propyl-substituted pyridin-2-yl guanidines were also prepared and studied.
    The Journal of Organic Chemistry 11/2011; 76(22):9216-27. · 4.45 Impact Factor
  • Article: 2001-2011: A Decade of the LADIS (Leukoaraiosis And DISability) Study: What Have We Learned about White Matter Changes and Small-Vessel Disease?
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    ABSTRACT: Over the last 20 years, evidence about the clinical correlates of cerebral white matter changes (WMC; also called leukoaraiosis) has been accumulating. WMC are now listed among the neuroimaging expressions of cerebral small-vessel disease and are no longer considered an innocuous finding because they are associated, in cross-sectional surveys, with various disturbances and, in follow-up studies, with poor prognosis. The Leukoaraiosis And DISability (LADIS) study has contributed substantially to this body of knowledge. LADIS is a European multicenter collaboration that was started in 2001 with the aim of assessing the independent role of WMC in predicting disability in subjects aged 65-84. The main results of the LADIS study have been released in 2009 with the demonstration that severe WMC more than double the risk of transition from an autonomous to a dependent status after 3 years of follow-up. The LADIS study has also contributed more focused substudies assessing the possible role of WMC in the decline of cognitive and motor performances, depressive symptoms associated with aging and cerebrovascular diseases, urinary disturbances, and also the role of other brain lesions (lacunar infarcts, cerebral atrophy, and corpus callosum morphology). The LADIS study provides a good example of harmonization of instruments (MRI protocol, clinical, neuropsychological, and functional scales) within an international collaboration. Currently, the LADIS study is providing data about the natural history of WMC. In this paper, we review the background and the main results of the LADIS study. This review puts forward some considerations for future studies in the field.
    Cerebrovascular Diseases 01/2011; 32(6):577-588. · 2.72 Impact Factor