Hong Kong medical journal = Xianggang yi xue za zhi / Hong Kong Academy of Medicine, 2012
To investigate the safety and efficacy of stroke thrombolysis in a local hospital. Historical coh... more To investigate the safety and efficacy of stroke thrombolysis in a local hospital. Historical cohort study. A tertiary hospital in Hong Kong. The outcome of acute ischaemic stroke patients treated with intravenous tissue plasminogen activator between October 2008 and May 2011 was compared to those admitted during the same period who were thrombolysis-eligible, but treated conservatively due to unavailability of the thrombolysis service after-hours. Intravenous tissue plasminogen activator. Primary outcome was functional independence (modified Rankin Scale score of 2 or below) at 3 months. Safety outcomes were symptomatic intracranial haemorrhage and 3-month mortality. Secondary outcomes were hospital length of stay, direct home discharge, and nursing home discharge. A total of 48 thrombolysis and 63 non-thrombolysis patients were identified. Fifty-two percent of the thrombolysis group achieved functional independence compared to 24% of non-thrombolysis group (P=0.003), without signi...
The Hofstadter model is a simple yet powerful Hamiltonian to study quantum Hall physics in a latt... more The Hofstadter model is a simple yet powerful Hamiltonian to study quantum Hall physics in a lattice system, manifesting its essential topological states. Lattice dimerization in the Hofstadter model opens an energy gap at half filling. Here we show that even if the ensuing insulator has a Chern number equal to zero, concomitantly a doublet of edge states appear that are pinned at specific momenta. We demonstrate that these states are topologically protected by inversion symmetry in specific one-dimensional cuts in momentum space, define and calculate the corresponding invariants, and identify a platform for the experimental detection of these novel topological states.
Platelets are known to participate in vascular pathologies; however, their role in neuroinflammat... more Platelets are known to participate in vascular pathologies; however, their role in neuroinflammatory diseases such as multiples sclerosis (MS) is unknown. Autoimmune CD4 T cells have been the main focus of studies of MS, although the factors that regulate T cell differentiation towards pathogenic Th1/Th17 phenotypes are not completely understood. We investigated the role of platelets in the modulation of CD4 T cell functions in MS patients and in mice with experimental autoimmune encephalitis (EAE), an animal model for MS. We found that early in MS and EAE platelets degranulated and produced a number of soluble factors serotonin (5HT), PF4 and PAF, which specifically stimulated differentiation of T cells towards pathogenic Th1, Th17 and IFN-γ/IL-17-producing CD4 T cells. At the later stages of MS and EAE platelets became exhausted in their ability to produce proinflammatory factors and stimulate CD4 T cells, but substantially increased their ability to form aggregates with CD4 T cells. Formation of platelet-CD4 T cell aggregates involved interaction of CD62P on activated platelets with adhesion molecule CD166 on activated CD4 T cells, contributing to downmodulation of CD4 T cell activation, proliferation and production of IFN-γ. Blocking of formation of platelet-CD4 T cell aggregates during progression of EAE substantially enhanced proliferation of CD4 T cell in the CNS and the periphery leading to exacerbation of the disease. Our study indicates differential roles for platelets in the regulation of functions of pathogenic CD4 T cells during initiation and progression of CNS autoimmune inflammation.
Platelets are known to participate in vascular pathologies; however, their role in neuroinflammat... more Platelets are known to participate in vascular pathologies; however, their role in neuroinflammatory diseases such as multiples sclerosis (MS) is unknown. Autoimmune CD4 T cells have been the main focus of studies of MS, although the factors that regulate T cell differentiation towards pathogenic Th1/Th17 phenotypes are not completely understood. We investigated the role of platelets in the modulation of CD4 T cell functions in MS patients and in mice with experimental autoimmune encephalitis (EAE), an animal model for MS. We found that early in MS and EAE platelets degranulated and produced a number of soluble factors serotonin (5HT), PF4 and PAF, which specifically stimulated differentiation of T cells towards pathogenic Th1, Th17 and IFN-γ/IL-17-producing CD4 T cells. At the later stages of MS and EAE platelets became exhausted in their ability to produce proinflammatory factors and stimulate CD4 T cells, but substantially increased their ability to form aggregates with CD4 T cel...
Journal of clinical and experimental neuropsychology, 2015
Vascular cognitive impairment (VCI) refers to the entire spectrum of cognitive dysfunction attrib... more Vascular cognitive impairment (VCI) refers to the entire spectrum of cognitive dysfunction attributable to vascular changes in the brain. The objective of this study is to evaluate magnetic resonance imaging (MRI) correlates of performance on the National Institute of Neurological Disorders and Stroke-Canadian Stroke Network (NINDS-CSN) VCI neuropsychology protocols. Fifty ischemic stroke patients and 50 normal elderly persons completed the VCI protocols and MRI. Relationships between the four cognitive domains (executive/activation, language, visuospatial, and memory) and three protocol (60-, 30-, and 5-min) summary scores with MRI measures of volumes of white matter hyperintensities (WMH) and global brain and hippocampal atrophy were assessed using linear regression. All cognitive domain scores were associated with WMH volume and, with the exception of language domain, with global atrophy. Additional relationships were found between executive/activation and language domains with l...
Dementia and geriatric cognitive disorders, Jan 12, 2015
We explored the association between cerebral microbleeds (CMBs) and cognitive impairment in patie... more We explored the association between cerebral microbleeds (CMBs) and cognitive impairment in patients with ischemic stroke/transient ischemic attack (TIA). A total of 488 ischemic stroke/TIA patients received magnetic resonance imaging. Montreal Cognitive Assessment (MoCA) was used to evaluate global cognitive function and cognitive domains. The association of CMB quantity with cognitive function and the impact of CMB locations (strictly lobar, strictly deep, and mixed regions) on cognitive impairment were examined in regression models with adjustments for confounders. A total of 113 subjects (23.2%) had ≥1 CMB. Strictly lobar, strictly deep, and mixed CMBs were identified in 36, 40, and 37 patients, respectively. The presence of ≥5 CMBs or strictly deep CMBs was associated with the MoCA total score (p = 0.007 and 0.020, respectively). Of all MoCA domains tested, a lower score in the attention domain was related to the presence of ≥5 CMBs (p = 0.014) and strictly deep CMBs (p = 0.028...
The authors hypothesized that both high and low pulse pressure (PP) may predict cognitive decline... more The authors hypothesized that both high and low pulse pressure (PP) may predict cognitive decline in stroke/transient ischemic attack (TIA) patients with white matter changes (WMCs). The authors prospectively followed up 406 ischemic stroke/TIA patients with confluent WMCs over 18Â months. PP was measured at 3 to 6Â months after stroke/TIA and categorized into four groups by quartile. Cognition was assessed 3 to 6Â months and 15 to 18Â months after stroke/TIA using the Clinical Dementia Rating and Mini-Mental State Examination (MMSE). Logistic regression showed that patients in the first quartile of PP had a 5.9-fold higher risk for developing cognitive decline than patients in the third quartile (odds ratio, 5.9; 95% confidence interval, 1.7-20.6), while patients in the fourth quartile had a 3.5-fold higher risk for cognitive decline than those in the third quartile (odds ratio, 3.5; 95% confidence interval, 1.0-12.4). This U-shaped relationship was also evident between PP and cognitive decline in MMSE, underlining the role of arterial stiffness and hypoperfusion in cognitive decline related to small vessel disease.
ABSTRACT The nontrivial topology of the electronic structure of iron pnictides can lead to the ap... more ABSTRACT The nontrivial topology of the electronic structure of iron pnictides can lead to the appearance of surface states. We study such states in various strip geometries with a focus on the superconducting phase. In the presence of unconventional superconducting pairing with $s_\pm$-wave gap structure, the topological states are quite robust and partly remain in the superconducting gap. Furthermore, Andreev bound states appear, which coexist with the topological states for small superconducting gaps and merge with them for larger gap values. The bulk and surface dispersions are obtained from exact diagonalization for two-orbital and five-orbital models in strip geometries.
Hong Kong medical journal = Xianggang yi xue za zhi / Hong Kong Academy of Medicine, 2010
To assess time management of stroke thrombolysis triage and functional outcomes in patients recei... more To assess time management of stroke thrombolysis triage and functional outcomes in patients receiving recombinant tissue plasminogen activator for hyperacute stroke, and identify bottlenecks in delivery of the treatment. Prospective study. A university teaching hospital in Hong Kong. Patients with suspected hyperacute stroke referred to the stroke thrombolysis team during October 2008 to September 2009. Time performance records including door-to-stroke team, door-to-needle, and onset-to-thrombolysis times. Functional outcomes by modified Rankin Scale score at 3 months, and thrombolysis-related complications including haemorrhagic transformations and mortality. During the 12-month period, 95 thrombolysis calls were received; recombinant tissue plasminogen activator was given intravenously to 17 (18%) of the patients and intra-arterially to 11 (12%). The mean (standard deviation) door-to-stroke team and the door-to-needle times for intravenous recombinant tissue plasminogen activator ...
Hong Kong medical journal = Xianggang yi xue za zhi / Hong Kong Academy of Medicine, 2011
Page 1. 168 Hong Kong Med J Vol 17 No 2 # April 2011 # www.hkmj.org Thrombolysis for acute ischae... more Page 1. 168 Hong Kong Med J Vol 17 No 2 # April 2011 # www.hkmj.org Thrombolysis for acute ischaemic stroke is evidence-based LETTER TO THEEDITOR To the Editor—We thank Professors Kumana and Cheung1 for their interest in our article. ...
To investigate whether asymptomatic middle cerebral artery (MCA) stenosis is associated with risk... more To investigate whether asymptomatic middle cerebral artery (MCA) stenosis is associated with risk of cardiovascular disease (CVD) in Chinese with type 2 diabetes. In this prospective cohort study, 2,144 Hong Kong Chinese with type 2 diabetes and without history of stroke or atrial fibrillation were recruited in 1994-1996 and followed up for a median of 14.51 years. Participants were assessed at baseline for MCA stenosis using transcranial Doppler. We performed survival analysis to assess the association between asymptomatic MCA stenosis and first CVD event, defined as ischemic stroke, acute coronary syndrome (ACS) or cardiovascular death. Of the 2,144 subjects, MCA stenosis at baseline was detected in 264 (12.3%). Rates of stroke, ACS and cardiovascular death per 100 were, respectively, 2.24, 2.92 and 1.11 among participants with stenosis, higher than among those without stenosis. Ten-year cumulative occurrence of stroke, ACS and cardiovascular death in subjects with MCA stenosis wa...
Hong Kong medical journal = Xianggang yi xue za zhi / Hong Kong Academy of Medicine, 2012
To investigate the safety and efficacy of stroke thrombolysis in a local hospital. Historical coh... more To investigate the safety and efficacy of stroke thrombolysis in a local hospital. Historical cohort study. A tertiary hospital in Hong Kong. The outcome of acute ischaemic stroke patients treated with intravenous tissue plasminogen activator between October 2008 and May 2011 was compared to those admitted during the same period who were thrombolysis-eligible, but treated conservatively due to unavailability of the thrombolysis service after-hours. Intravenous tissue plasminogen activator. Primary outcome was functional independence (modified Rankin Scale score of 2 or below) at 3 months. Safety outcomes were symptomatic intracranial haemorrhage and 3-month mortality. Secondary outcomes were hospital length of stay, direct home discharge, and nursing home discharge. A total of 48 thrombolysis and 63 non-thrombolysis patients were identified. Fifty-two percent of the thrombolysis group achieved functional independence compared to 24% of non-thrombolysis group (P=0.003), without signi...
The Hofstadter model is a simple yet powerful Hamiltonian to study quantum Hall physics in a latt... more The Hofstadter model is a simple yet powerful Hamiltonian to study quantum Hall physics in a lattice system, manifesting its essential topological states. Lattice dimerization in the Hofstadter model opens an energy gap at half filling. Here we show that even if the ensuing insulator has a Chern number equal to zero, concomitantly a doublet of edge states appear that are pinned at specific momenta. We demonstrate that these states are topologically protected by inversion symmetry in specific one-dimensional cuts in momentum space, define and calculate the corresponding invariants, and identify a platform for the experimental detection of these novel topological states.
Platelets are known to participate in vascular pathologies; however, their role in neuroinflammat... more Platelets are known to participate in vascular pathologies; however, their role in neuroinflammatory diseases such as multiples sclerosis (MS) is unknown. Autoimmune CD4 T cells have been the main focus of studies of MS, although the factors that regulate T cell differentiation towards pathogenic Th1/Th17 phenotypes are not completely understood. We investigated the role of platelets in the modulation of CD4 T cell functions in MS patients and in mice with experimental autoimmune encephalitis (EAE), an animal model for MS. We found that early in MS and EAE platelets degranulated and produced a number of soluble factors serotonin (5HT), PF4 and PAF, which specifically stimulated differentiation of T cells towards pathogenic Th1, Th17 and IFN-γ/IL-17-producing CD4 T cells. At the later stages of MS and EAE platelets became exhausted in their ability to produce proinflammatory factors and stimulate CD4 T cells, but substantially increased their ability to form aggregates with CD4 T cells. Formation of platelet-CD4 T cell aggregates involved interaction of CD62P on activated platelets with adhesion molecule CD166 on activated CD4 T cells, contributing to downmodulation of CD4 T cell activation, proliferation and production of IFN-γ. Blocking of formation of platelet-CD4 T cell aggregates during progression of EAE substantially enhanced proliferation of CD4 T cell in the CNS and the periphery leading to exacerbation of the disease. Our study indicates differential roles for platelets in the regulation of functions of pathogenic CD4 T cells during initiation and progression of CNS autoimmune inflammation.
Platelets are known to participate in vascular pathologies; however, their role in neuroinflammat... more Platelets are known to participate in vascular pathologies; however, their role in neuroinflammatory diseases such as multiples sclerosis (MS) is unknown. Autoimmune CD4 T cells have been the main focus of studies of MS, although the factors that regulate T cell differentiation towards pathogenic Th1/Th17 phenotypes are not completely understood. We investigated the role of platelets in the modulation of CD4 T cell functions in MS patients and in mice with experimental autoimmune encephalitis (EAE), an animal model for MS. We found that early in MS and EAE platelets degranulated and produced a number of soluble factors serotonin (5HT), PF4 and PAF, which specifically stimulated differentiation of T cells towards pathogenic Th1, Th17 and IFN-γ/IL-17-producing CD4 T cells. At the later stages of MS and EAE platelets became exhausted in their ability to produce proinflammatory factors and stimulate CD4 T cells, but substantially increased their ability to form aggregates with CD4 T cel...
Journal of clinical and experimental neuropsychology, 2015
Vascular cognitive impairment (VCI) refers to the entire spectrum of cognitive dysfunction attrib... more Vascular cognitive impairment (VCI) refers to the entire spectrum of cognitive dysfunction attributable to vascular changes in the brain. The objective of this study is to evaluate magnetic resonance imaging (MRI) correlates of performance on the National Institute of Neurological Disorders and Stroke-Canadian Stroke Network (NINDS-CSN) VCI neuropsychology protocols. Fifty ischemic stroke patients and 50 normal elderly persons completed the VCI protocols and MRI. Relationships between the four cognitive domains (executive/activation, language, visuospatial, and memory) and three protocol (60-, 30-, and 5-min) summary scores with MRI measures of volumes of white matter hyperintensities (WMH) and global brain and hippocampal atrophy were assessed using linear regression. All cognitive domain scores were associated with WMH volume and, with the exception of language domain, with global atrophy. Additional relationships were found between executive/activation and language domains with l...
Dementia and geriatric cognitive disorders, Jan 12, 2015
We explored the association between cerebral microbleeds (CMBs) and cognitive impairment in patie... more We explored the association between cerebral microbleeds (CMBs) and cognitive impairment in patients with ischemic stroke/transient ischemic attack (TIA). A total of 488 ischemic stroke/TIA patients received magnetic resonance imaging. Montreal Cognitive Assessment (MoCA) was used to evaluate global cognitive function and cognitive domains. The association of CMB quantity with cognitive function and the impact of CMB locations (strictly lobar, strictly deep, and mixed regions) on cognitive impairment were examined in regression models with adjustments for confounders. A total of 113 subjects (23.2%) had ≥1 CMB. Strictly lobar, strictly deep, and mixed CMBs were identified in 36, 40, and 37 patients, respectively. The presence of ≥5 CMBs or strictly deep CMBs was associated with the MoCA total score (p = 0.007 and 0.020, respectively). Of all MoCA domains tested, a lower score in the attention domain was related to the presence of ≥5 CMBs (p = 0.014) and strictly deep CMBs (p = 0.028...
The authors hypothesized that both high and low pulse pressure (PP) may predict cognitive decline... more The authors hypothesized that both high and low pulse pressure (PP) may predict cognitive decline in stroke/transient ischemic attack (TIA) patients with white matter changes (WMCs). The authors prospectively followed up 406 ischemic stroke/TIA patients with confluent WMCs over 18Â months. PP was measured at 3 to 6Â months after stroke/TIA and categorized into four groups by quartile. Cognition was assessed 3 to 6Â months and 15 to 18Â months after stroke/TIA using the Clinical Dementia Rating and Mini-Mental State Examination (MMSE). Logistic regression showed that patients in the first quartile of PP had a 5.9-fold higher risk for developing cognitive decline than patients in the third quartile (odds ratio, 5.9; 95% confidence interval, 1.7-20.6), while patients in the fourth quartile had a 3.5-fold higher risk for cognitive decline than those in the third quartile (odds ratio, 3.5; 95% confidence interval, 1.0-12.4). This U-shaped relationship was also evident between PP and cognitive decline in MMSE, underlining the role of arterial stiffness and hypoperfusion in cognitive decline related to small vessel disease.
ABSTRACT The nontrivial topology of the electronic structure of iron pnictides can lead to the ap... more ABSTRACT The nontrivial topology of the electronic structure of iron pnictides can lead to the appearance of surface states. We study such states in various strip geometries with a focus on the superconducting phase. In the presence of unconventional superconducting pairing with $s_\pm$-wave gap structure, the topological states are quite robust and partly remain in the superconducting gap. Furthermore, Andreev bound states appear, which coexist with the topological states for small superconducting gaps and merge with them for larger gap values. The bulk and surface dispersions are obtained from exact diagonalization for two-orbital and five-orbital models in strip geometries.
Hong Kong medical journal = Xianggang yi xue za zhi / Hong Kong Academy of Medicine, 2010
To assess time management of stroke thrombolysis triage and functional outcomes in patients recei... more To assess time management of stroke thrombolysis triage and functional outcomes in patients receiving recombinant tissue plasminogen activator for hyperacute stroke, and identify bottlenecks in delivery of the treatment. Prospective study. A university teaching hospital in Hong Kong. Patients with suspected hyperacute stroke referred to the stroke thrombolysis team during October 2008 to September 2009. Time performance records including door-to-stroke team, door-to-needle, and onset-to-thrombolysis times. Functional outcomes by modified Rankin Scale score at 3 months, and thrombolysis-related complications including haemorrhagic transformations and mortality. During the 12-month period, 95 thrombolysis calls were received; recombinant tissue plasminogen activator was given intravenously to 17 (18%) of the patients and intra-arterially to 11 (12%). The mean (standard deviation) door-to-stroke team and the door-to-needle times for intravenous recombinant tissue plasminogen activator ...
Hong Kong medical journal = Xianggang yi xue za zhi / Hong Kong Academy of Medicine, 2011
Page 1. 168 Hong Kong Med J Vol 17 No 2 # April 2011 # www.hkmj.org Thrombolysis for acute ischae... more Page 1. 168 Hong Kong Med J Vol 17 No 2 # April 2011 # www.hkmj.org Thrombolysis for acute ischaemic stroke is evidence-based LETTER TO THEEDITOR To the Editor—We thank Professors Kumana and Cheung1 for their interest in our article. ...
To investigate whether asymptomatic middle cerebral artery (MCA) stenosis is associated with risk... more To investigate whether asymptomatic middle cerebral artery (MCA) stenosis is associated with risk of cardiovascular disease (CVD) in Chinese with type 2 diabetes. In this prospective cohort study, 2,144 Hong Kong Chinese with type 2 diabetes and without history of stroke or atrial fibrillation were recruited in 1994-1996 and followed up for a median of 14.51 years. Participants were assessed at baseline for MCA stenosis using transcranial Doppler. We performed survival analysis to assess the association between asymptomatic MCA stenosis and first CVD event, defined as ischemic stroke, acute coronary syndrome (ACS) or cardiovascular death. Of the 2,144 subjects, MCA stenosis at baseline was detected in 264 (12.3%). Rates of stroke, ACS and cardiovascular death per 100 were, respectively, 2.24, 2.92 and 1.11 among participants with stenosis, higher than among those without stenosis. Ten-year cumulative occurrence of stroke, ACS and cardiovascular death in subjects with MCA stenosis wa...
Uploads
Papers by Alexander Lau