Sodium dodecyl sulfate-insoluble oligomers are involved in polyglutamine degeneration

In polyglutamine (polyQ) degeneration, disease protein that carries an expanded polyQ tract is neurotoxic. Expanded polyQ protein exists in different conformations that display distinct solubility properties. In this study, an inducible transgenic Drosophila model is established to define the pathogenic form of polyQ protein at an early stage of degeneration in vivo. We show that microscopic polyQ aggregates are neither pathogenic nor protective. Further, no toxic effect of sodium dodecyl sulfate (SDS) -soluble polyQ protein is observed in our model. By means of filtration, 2 forms of SDS-insoluble protein species are identified according to their size. Coexpression of an ATPase-defective form of the molecular chaperone Hsc70 (Hsc70-K71S) selectively reduces the abundance of the large SDS-insoluble polyQ species, but such modulation has no modifying effects on degeneration. Notably, we detect a distinct Hsc70-K71S-resistant, small, SDS-insoluble polyQ oligomeric species that is closely correlated with degeneration. Our data highlight the toxic role of SDS-insoluble oligomers in polyQ degeneration in vivo.

Prevalence of clinically significant depressive symptoms in an epidemiologic sample of community-dwelling elders with milder forms of cognitive impairment in Hong Kong SAR

BACKGROUND

Depression and cognitive impairment in later-life have great bearings on public health. The two conditions often co-occur and have mutual implications on short-term risk and long-term prognosis.

METHOD

A two-phase epidemiologic survey on the prevalence of dementia in elders aged 60 and over was conducted in Hong Kong in 2005-2006. In the first phase, 6,100 randomly selected community dwelling elders were assessed with Cantonese version of Mini-Mental State Examination (C-MMSE) and Abbreviated Memory Inventory for Chinese (AMIC). Two thousand and seventy-three subjects were screened positive and invited for second phase cognitive and psychiatric assessment. 35.5% of screen-positive subjects participated in Phase 2 assessment conducted by psychiatrists for diagnosis of dementia. Severity of dementia was determined using Clinical Dementia Rating Scale (CDR). Cornell Scale for Depression in Dementia (CSDD) and a structured bedside cognitive battery were also administered to each subject.

RESULTS

1.7% of subjects with CDR 0.5 and 5.9% of subjects with CDR 1 had clinically significant depressive symptoms (>or= 8 on CSDD). Score on CSDD correlated positively with duration of cognitive symptoms, scores on CIRS and CMMSE in linear regression model. In a logistic regression model, male gender, duration of cognitive symptoms, CIRS and CMMSE was associated with increased risk for clinically significant depressive symptoms.

CONCLUSIONS

In our sample, milder forms of cognitive impairment were associated with increased risk for depression in the presence of other risk factors such as male gender, higher physical illness burden and longer duration of cognitive symptoms.

Prevalence of very mild and mild dementia in community-dwelling older Chinese people in Hong Kong

INTRODUCTION

In this report, the results of a household survey were used to examine the prevalence of very mild and mild dementia in Chinese older persons in Hong Kong.

METHODS

The study adopted a two-phase design. At Phase 1, 6100 subjects were screened using the Cantonese version of the Mini-mental State Examination (MMSE) and a short memory inventory. At Phase 2, 2073 subjects were screened positive and 737 were evaluated by psychiatrists. Clinical Dementia Rating (CDR) and cognitive assessment were used for diagnosis of dementia. Very mild dementia (VMD) was defined as a global CDR of 0.5, with memory and non-memory subscale scores of 0.5 or more. Mild dementia was classified for subjects with a CDR of 1.

RESULTS

The overall prevalence of VMD and mild dementia for persons aged 70 years or above was 8.5% (95%CI: 7.4-9.6) and 8.9% (95%CI: 7.8-10.0) respectively. Among subjects with clinical dementia, 84.6% had mild (CDR1) dementia. Logistic regression analyses revealed that older age, lower educational level and significant cerebrovascular risk factors were risk factors for dementia, while regular physical exercise was a protective factor for dementia.

CONCLUSIONS

A sizable proportion of community-living subjects suffered from milder forms of dementia. They represent a high risk for early intervention to reduce potential physical and psychiatric morbidity.

Screening of mild cognitive impairment in Chinese older adults--a multistage validation of the Chinese abbreviated mild cognitive impairment test

OBJECTIVE

To develop a short cognitive test for screening mild cognitive impairment (MCI) in Hong Kong Chinese older adults.

METHODS

The Chinese Abbreviated MCI (CAMCI) test was developed with a multistage process. In phase 1, a short version of the cognitive test comprising a 1-min animal fluency test and a 10-min delayed word list recall was developed and tested in 578 volunteers (community-dwelling active elderly persons). In phase 2, the CAMCI test was validated in an independent and randomly recruited sample of 459 participants in a community survey. Additionally, the predictive significance of the CAMCI test was evaluated in a group of 196 subjects assessed in phase 1 for conversion to clinical dementia at 20 months' follow-up. The discriminating power of the CAMCI test in differentiating MCI from normal control (NC) and mildly demented subjects was compared with Mini Mental State Examination (MMSE) and Alzheimer's Disease Assessment Scale-Cognitive (ADAS-Cog) subscales.

RESULTS

The CAMCI test was found to have high discriminating power in differentiating NC from MCI and mildly demented subjects in the phase 1 volunteer sample. The receiver operating characteristics (ROC) revealed an area under the curve (AUC) of 0.91. The ROC were further validated in the phase 2 sample. The AUC of the CAMCI test was compared with MMSE and ADAS-Cog subscales. The short MCI test was comparable to the ADAS-Cog subscale in discriminating NC from MCI and demented subjects (chi(2) test, p = n.s.). Logistic regression analysis was carried out to determine significant baseline predictors for conversion to dementia at phase 3 follow-up. Both ADAS-Cog total [Exp(B) = 1.115, p = 0.028] and CAMCI [Exp(B) = 0.88, p = 0.045] scores were significant predictors for dementia status at follow-up.

CONCLUSION

The CAMCI test is able to discriminate NC from MCI and mild dementia in Hong Kong Chinese older adults. Its potential for large-scale community screening for early detection of cognitive impairment in late life should be emphasized and explored.

A green fluorescent protein-based reporter for protein nuclear import studies in Drosophila cells

Green fluorescent protein-based reporters are commonly used to investigate protein nucleocytoplasmic transport. In this study we developed a novel reporter GFP2-GST which consists of two copies of GFP and one copy of GST, and tested it in two commonly used Drosophila cell lines. The size of the GFP2-GST reporter exceeds the passive diffusion limit across the nuclear pore complexes. It shows an exclusive cytoplasmic localization and displays a restrictive nuclear localization when a nuclear localization signal is appended. This reporter will largely facilitate the characterization and identification of NLS sequences in the fly proteome.

A novel missense RP1 mutation in retinitis pigmentosa

AIMS

More than 20 mutations associated with retinitis pigmentosa (RP) have been identified in the retinitis pigmentosa 1 (RP1) gene, all of them leading to the production of a truncated protein without 50-70% of the C-terminal of the RP1 protein. RP1 was recently found to be a microtubule-associated protein (MAP) and responsible for the organisation of the photoreceptor outer segment. The N-terminal doublecortin (DCX) domain of RP1 is essential for its function. But how the C-terminal of the protein affects its function is still not known. This study aims to get a better understanding of the RP1 gene by mutation screening on RP patients.

METHODS

Peripheral blood was taken from 72 RP patients. Together with 101 RP patients and 190 control subjects previously reported, mutation screening was performed by polymerase chain reaction (PCR) and direct sequencing. Statistical analysis was performed using SPSS.

RESULTS

Two novel missense sequence changes, D984G and C727W, and one novel variant, 6492T>G, at the 3' untranslated region were found. They were not found in 190 control subjects. D984G causes RP. It creates two possible N-myristoylation sites according to PROSITE. C727W does not segregate with RP in the family. It abolishes an N-myristoylation site. R872H, a previously reported polymorphism, was predominantly present in control subjects (P=0.001).

CONCLUSIONS

Our results suggest that disruption of the C-terminal of RP1 may be associated with the development of RP, and the possible involvement of the RP1 polypeptide downstream of its DCX domain in normal RP1 function.

A novel genetic study of Chinese families with autosomal recessive retinitis pigmentosa

Autosomal recessive retinitis pigmentosa (arRP) is the commonest form of RP worldwide. To date 22 loci have been implicated in the pathogenesis of this disease; however none of these loci independently account for a significant proportion of recessive RP. Linkage studies of arRP in consanguineous families have been mainly based on homozygosity mapping, but this strategy cannot be applied in the case of non-consanguineous families. Therefore, we implemented a systematic approach for identifying the disease locus in three non-consanguineous Chinese families with arRP. Initially, linkage analysis using SNPs/microsatellite markers or mutation screening of known arRP genes excluded all loci/genes except RP25 on chromosome 6. Subsequently a whole genome scan for the three families using the 10K GeneChip Mapping Array was performed, in order to identify the possible disease locus. To the best of our knowledge this is the first report on the utilisation of the 10K GeneChip to study linkage in non-consanguineous Chinese arRP. This analysis indicates that the studied families are probably linked to the RP25 locus, a well defined arRP locus in other populations. The identification of another ethnic group linked to RP25 is highly suggestive that this represents a major locus for arRP.

Prevalence of subclinical infection and transmission of severe acute respiratory syndrome (SARS) in a residential care home for the elderly

OBJECTIVE

To ascertain the prevalence of subclinical severe acute respiratory syndrome-coronavirus (SARS-CoV) infection and study the transmission of SARS-CoV in a local outbreak at a residential care home for the elderly.

DESIGN

Cross-sectional study.

SETTING

A residential care home for the elderly in Hong Kong with a local outbreak of SARS.

PARTICIPANTS

Residents and staff in the residential care home who had contact with three patients with SARS (residents A and B, and staff C).

MAIN OUTCOME MEASURES

Blood samples were tested for total antibodies to SARS-CoV by immunofluorescence antibody test. The transmission of SARS was elucidated based on information from standardised questionnaires, and records of investigation and surveillance by the Department of Health.

RESULTS

Among the 90 eligible residents, three died, one moved out, and 19 refused to participate. Of the 32 eligible staff, six refused to participate. None of the remaining 93 participants tested positive for antibody to SARS-CoV. Based on the chronological order, resident A might have transmitted infection to resident B and staff C. Sitting close to the bathroom doorway while resident A took a shower was the only contact of resident B with resident A. The only opportunity for staff C to have contact with body fluids/excreta of resident A was in the handling of rubbish from the resident's room.

CONCLUSION

Subclinical SARS-CoV infection was rare in a residential care home for the elderly with an outbreak of SARS. Nonetheless the close working and living conditions for staff and residents in such a home may facilitate transmission of SARS despite vigilant precautionary measures.

Second eye of patients with unilateral neovascular age-related macular degeneration: Caucasians vs Chinese

PURPOSE

To investigate the correlation between morphological features of choroidal neovascularisation (CNV) secondary to age-related macular degeneration (AMD) in the first eye and the severity of age-related maculopathy (ARM) in the fellow eyes in two racial groups: Caucasians and Chinese.

PARTICIPANTS

A total of 135, fluorescein angiograms of patients with unilateral neovascular AMD and ARM in the fellow eyes were included in the study: 38 Caucasians from King's College Hospital, UK; 45 Caucasians from West Kent Eye Centre, UK; 52 Chinese from Hong Kong Eye Hospital, Hong Kong.

MAIN OUTCOME MEASURES

CNV subtype in the affected eye and ARM severity in the second eyes.

RESULTS

Although the proportion of CNV subtypes in the three groups were similar, the Chinese cohort showed significantly less ARM severity compared to the Caucasian cohorts (P < 0.05).

CONCLUSION

Although drusen and retinal pigmentary changes may be prognostic indicators of CNV, this study suggest that other factors contribute significantly to the pathogenesis of CNV in AMD.

Genetic markers for retinitis pigmentosa

OBJECTIVE

To review recent advances in the molecular genetics of retinitis pigmentosa with emphasis on the development of genetic markers that aids diagnosis and prognosis.

DATA SOURCES AND EXTRACTION

Literature search of MEDLINE from 1988 to 2005 using the following key words: 'retinitis pigmentosa', 'rhodopsin', 'RP1', 'RPGR', and 'genetic counseling'. References of two genes--RHO and RP1--causing retinitis pigmentosa in the Chinese population were reviewed.

STUDY SELECTION

Literature and data related to genetic markers for retinitis pigmentosa.

DATA SYNTHESIS

The genetics of retinitis pigmentosa is complex. It can be sporadic or familial, with heterogeneous transmission modes. Retinitis pigmentosa is associated with nearly 40 chromosomal loci, where 32 candidate genes have been identified. A large number of mutations are known to cause retinitis pigmentosa. But no single mutation alone accounts for more than 10% of unrelated retinitis pigmentosa patients. Genetic tests for retinitis pigmentosa require screening for a consort of mutations in a large number of genes. High throughput screening technology such as denaturing high performance liquid chromatography and automated DNA sequencing should make such tests feasible.

CONCLUSIONS

Rapid developments in the understanding of the genetics of retinitis pigmentosa have helped to establish genetic tests of clinical value. The complex mode of inheritance nonetheless makes genetic counselling difficult, even in the presence of positive genetic screening results.

Gene mutations in retinitis pigmentosa and their clinical implications

Retinitis pigmentosa (RP) is a group of inherited progressive retinal diseases affecting about 1 in 3500 people worldwide. So far, there is no prevention or cure, with permanent visual loss or even blindness the ultimate consequence usually after midlife. The genetics of RP are complex. It can be sporadic, autosomal dominant, autosomal recessive, or X-linked. Thirty-two genes are known to be associated with RP, sometimes the same gene gets involved in different inheritance traits. Some RP cases have a digenic cause. About 60% RP cases still have no known genetic cause. A large number of mutations cause RP, and they can be deletions, insertions, or substitutions that cause missense mutations or truncations. The RHO, RP1, and RPGR genes contribute the greatest number of known mutations causative of RP. But there is no single mutation that alone accounts for more than 10% of unrelated patients. Genetic testing for RP therefore requires screening for a group of genes. High-throughput and automated sequence detection technologies are essential. Due to the complexity in phenotype and genetics, and the fact that RP is untreatable, genetic testing for presymptomatic diagnosis of RP is controversial. Meanwhile, new genes are still to be identified, mostly by family linkage and sib-pair analysis. Research on gene therapy for RP requires information on gene mutations causative of RP.

Modified endoscopic dacryocystorhinostomy with posterior lacrimal sac flap for nasolacrimal duct obstruction

OBJECTIVES

To evaluate a new technique of modified endoscopic dacryocystorhinostomy involving the creation of a large posterior flap at the lacrimal sac and to compare its success rate with that of the conventional endoscopic method of excising the entire medial lacrimal sac wall as a surgical treatment for epiphora caused by nasolacrimal duct obstruction.

DESIGN

Retrospective, interventional, and comparative case series.

SETTING

University teaching hospital, Hong Kong.

PATIENTS AND METHODS

Only adults with primary nasolacrimal duct obstruction were included. Consecutive endoscopic dacryocystorhinostomy was performed using two different techniques from July 1999 to June 2001. The new technique involved the creation of a large posterior flap at the medial lacrimal sac wall, reflecting it posteriorly, followed by removal of the remaining small anterior flap (the LSF group). Other patients had the entire medial lacrimal sac wall excised (the ELS group).

MAIN OUTCOME MEASURES

Surgical success was defined by free fluorescein drainage from the conjunctival sac into the rhinostomy site at least 3 months after silicone stent removal.

RESULTS

Ninety-nine procedures were performed in 99 patients. The success rate was 89.1% (41/46) in the LSF group and 71.7% (38/53) in the ELS group. The difference between the two groups was statistically significant (Chi squared test, P=0.031).

CONCLUSIONS

Our new and modified technique of endonasal dacryocystorhinostomy has a greater success rate than conventional endonasal dacryocystorhinostomy. A large-scale prospective randomised controlled trial to further evaluate the efficacy and safety of this surgical technique is under way.

Smoking and depressive symptoms in Chinese elderly in Hong Kong

OBJECTIVE

To examine the association between smoking and depressive symptoms among Chinese elderly in Hong Kong.

METHOD

Cross-sectional data on smoking and depressive symptoms from 56,167 Chinese elderly aged 65 or over in Hong Kong were analysed using logistic regression.

RESULTS

Current smokers and former smokers were more likely to have depressive symptoms than never smokers. The adjusted odds ratios (OR) and 95% confidence interval (CI) in males and females respectively were 1.62 (1.34-1.96) and 1.43 (1.20-1.70) for current smokers, and were 1.18 (0.99-1.40) and 1.29 (1.12-1.47) for former smokers. Former smokers were less likely to have depressive symptoms than current smokers (OR = 0.80, 95% CI: 0.70-0.92).

CONCLUSION

Smoking is positively associated with depressive symptoms in Chinese elderly. Health care workers should be vigilant about the detection of depressive symptoms in elderly smokers.

Red eyes as the initial presentation of systemic meningococcal infection

The present paper is a report of a 14-month-old boy who presented with fever, coryzal symptoms and red eyes. The patient developed a generalized tonic clonic convulsion on day 2 of his illness. Ophthalmological assessment demonstrated bilateral hypopyon and vitreous opacity resulting from endophthalmitis. Cerebrospinal fluid was positive for Neisseria meningitidis (A, C, Y, W 135) by latex agglutination. He was treated with high dose intravenous cefotaxime and intravitreal ceftazidime. He made good recovery and his vision was preserved. In view of the potential morbidity and mortality associated with systemic meningococcal infection, the presence of red eye and hypopyon provides important diagnostic clues indicating the need to investigate beyond superficial conjunctivitis. It should prompt the clinician to recognize endopthalmitis early and accurately diagnose this serious disease.

Unexplained recurrent pericardial effusion: a lethal warning?

A case of a 37 year old man with cardiac angiosarcoma causing recurrent pericardial effusion, who eventually died of cardiac rupture, is presented. The diagnosis was not established until the postmortem examination despite echocardiography, pericardiocentesis, and pericardial biopsy investigations. There is neither a specific manifestation that enables early recognition nor well proven effective treatment against this disease. Accordingly, the prognosis of cardiac angiosarcoma remains grave. A high index of suspicion is recommended in patients who present with unexplained pericardial effusion.

Grouping has a negative effect on both subjective contours and perceived occlusion at T-junctions

Perceived occlusion of aligned T-junctions and subjective contours at implicit T-junctions are often assumed to be related but are rarely examined with respect to common mechanisms. Using the method of paired comparison, we measured the strength of perceived occlusion at explicit T-junctions and the strength of subjective contours at implicit T-junctions (using different subjects) along the aligned edges of eight sets of inducer shapes. Sets varied in the similarity of component shapes with respect to orientation, height, width, and color With increasing shape similarity there was a striking decrease in both the strength of subjective contours and the strength of perceived occlusion; the correlation between these two kinds of judgments was .97. We conclude that common mechanisms underlie these two percepts and that edge alignment is a much stronger indicator of occlusion for poorly grouped than for strongly grouped inducers.

Molecular diagnostics for retinitis pigmentosa

BACKGROUND

At least 1 million people worldwide have retinitis pigmentosa (RP), making it relatively common among the inherited forms of blindness. Mutations in many genes may cause RP. The most common known mutation, Pro347Leu in rhodopsin, is found in no more than about 1% of unrelated patients, implying the impracticality of a diagnostic test which would screen only for a few, common mutation sites.

CONCLUSIONS

Ongoing discovery and study of RP genes makes it feasible to consider a molecular diagnostic test which would screen coding regions of all known RP genes by a mutation detection method such as conformation-sensitive gel electrophoresis followed by sequencing. The parallel development of RP genetic knowledge and treatments such as gene therapy will make such tests both possible and necessary.

Rhodopsin mutations in Chinese patients with retinitis pigmentosa

AIM

To determine the pattern of rhodopsin mutations in Chinese retinitis pigmentosa (RP) patients.

METHODS

The rhodopsin gene was examined in 101 RP patients and 190 controls from Hong Kong.

RESULTS

Three coding changes were identified: Pro347Leu, Ala299Ser, and 5211delC. Each protein sequence alteration was found in one patient. Ala299Ser also existed in two controls.

CONCLUSION

The C-terminal nonsense mutation may cause mis-sorting of rhodopsin protein. The finding of controls with Ala299Ser suggests this is only the third missense alteration reported that does not cause RP. The expected frequency of rhodopsin mutations in RP is <7% (2/101=2.0%, 95% confidence interval: 0.2%-7.0%).