Dosage of amyloid precursor protein affects axonal contact guidance in Down syndrome

Amyloid precursor protein (APP), encoded on Hsa21, functions as a cell adhesion molecule (CAM) in axonal growth cones (GCs) of the developing brain. We show here that axonal GCs of human fetal Down syndrome (DS) neurons (and of a DS mouse model) overexpress APP protein relative to euploid controls. We investigated whether DS neurons generate an abnormal, APP-dependent GC phenotype in vitro. On laminin, which binds APP and β1 integrins (Itgb1), DS neurons formed enlarged and faster-advancing GCs compared to controls. On peptide matrices that bind APP only, but not on those binding exclusively Itgb1 or L1CAM, DS GCs were significantly enlarged (2.0-fold), formed increased close adhesions (1.8-fold), and advanced faster (1.4-fold). In assays involving alternating stripes of monospecific matrices, human control GCs exhibited no preference for any of the substrates, whereas DS GCs preferred the APP-binding matrix (cross-over decreased significantly from 48.2 to 27.2%). Reducing APP expression in DS GCs with siRNA normalized most measures of the phenotype, including substrate choice. These experiments show that human DS neurons exhibit an APP-dependent, abnormal GC phenotype characterized by increased adhesion and altered contact guidance. The results suggest that APP overexpression may perturb axonal pathfinding and circuit formation in developing DS brain.

Frequency and circumstances of falls in people with inclusion body myositis: a questionnaire survey to explore falls management and physiotherapy provision

OBJECTIVES

To survey the incidence and circumstances of falls for people with inclusion body myositis (IBM) in the UK, and to investigate the provision of physiotherapy and falls management.

DESIGN

Postal questionnaire survey.

SETTING

Participants completed questionnaires at home.

PARTICIPANTS

Ninety-four people diagnosed with IBM were screened against the inclusion criteria. Seventy-two potential participants were sent a questionnaire, and 62 were completed and returned. Invited participants were sent an adapted Falls Event Questionnaire pertaining to falls, perceived causes of falls and the provision of physiotherapy. Questionnaires were returned anonymously.

MAIN OUTCOME MEASURES

The proportions of respondents who reported a fall or a near fall, along with the frequencies of falls and near falls were calculated. Descriptive data of falls were collected pertaining to location and cause. Data analysis was performed to investigate provision of physiotherapy services.

RESULTS

The response rate was 86% [62/72, mean (standard deviation) age 68 (8) years]. Falls were reported by 98% (61/62) of respondents, with 60% (37/62) falling frequently. In this study, age was not found to be an indicator of falls risk or frequency. Twenty-one percent (13/62) of respondents had not seen a physiotherapist in relation to their IBM symptoms, and of those that had, 31% (15/49) had not seen a physiotherapist until more than 12 months after IBM was diagnosed. Only 18% (11/61) of fallers reported that they had received falls management input.

CONCLUSIONS

Falls are a common occurrence for people with IBM, independent of age and years since symptoms first presented, and are poorly addressed by appropriate physiotherapy management. National falls guidelines are not being followed, and referral rates to physiotherapy need to improve.

Does mammographic density reflect the expression of breast cancer markers?

Mammographic density reflects variation in breast tissue composition as detected on mammogram. It is associated with a number of well-known breast cancer risk factors and itself is considered one of the strongest risk factors for breast cancer. If the expression of several proteins and genes within the breast tissue influences mammographic density in the same way as it influences breast cancer risk, then mammographic density might serve as an intermediate biomarker in future epidemiological studies on breast cancer. This has the potential to provide a quick means for predicting the effect of changes in the breast microenvironment on breast cancer risk without having to wait for an eventual development of breast cancer. In this review, the expression of several proteins and genes (growth factors, enzymes, proteoglycans and pro-inflammatory markers) within the breast tissue is shown to be associated with mammographic density. These proteins and genes are suspected to play a role in breast carcinogenesis. More studies assessing differential expression of proteins and genes in mammary epithelium and stroma and their association with mammographic density among premenopausal and postmenopausal women are required. Identification of proteins and genes influencing mammographic density may provide further insight on the molecular causes of breast cancer.

Assessing fitness to drive in brain tumour patients: a grey matter of law, ethics, and medicine

BACKGROUND

Neurocognitive deficits from brain tumours may impair the ability to safely operate a motor vehicle. Although certain jurisdictions in Canada legally require that physicians report patients who are unfit to drive, criteria for determining fitness are not clearly defined for brain tumours.

METHODS

Patients receiving brain radiotherapy at our institution from January to June 2009 were identified using the Oncology Patient Information System. In addition to descriptive statistics, details of driving assessment were reviewed retrospectively. The Fisher exact test was used to determine factors predictive of reporting a patient to the Ontario Ministry of Transportation (mto) as unfit to drive. A logistic regression model was constructed to further determine factors predictive of reporting.

RESULTS

Of the 158 patients available for analysis, 48 (30%) were reported to the mto, and 64 (41%) were advised to stop driving. With respect to the 53 patients with seizures, a report was submitted to the mto for 30 (57%), and a documented discussion about the implications of driving was held with 35 (66%). On univariate analysis, younger age, a central nervous system primary, higher brain radiotherapy dose, unifocal disease, and the presence of seizures were predictive of physician reporting (p < 0.05). On logistic regression modelling, the presence of seizures (odds ratio: 3.9) and a higher radiotherapy dose (odds ratio: 1.3) remained predictive of reporting.

INTERPRETATION

Physicians frequently do not discuss the implications of driving with brain tumour patients or are not properly documenting such advice (or both). Clear and concise reporting guidelines need to be drafted given the legal, medical, and ethical concerns surrounding this public health issue.

Multidisciplinary assessment of fitness to drive in brain tumour patients in southwestern Ontario: a grey matter

BACKGROUND

Neurocognitive impairments from brain tumours may interfere with the ability to drive safely. In 9 of 13 Canadian provinces and territories, physicians have a legal obligation to report patients who may be medically unfit to drive. To complicate matters, brain tumour patients are managed by a multidisciplinary team; the physician most responsible to make the report of unfitness is often not apparent. The objective of the present study was to determine the attitudes and reporting practices of physicians caring for these patients.

METHODS

A 17-question survey distributed to physicians managing brain tumour patients elicited Respondent demographicsKnowledge about legislative requirementsExperience of reportingBarriers and attitudes to reporting Fisher exact tests were performed to assess differences in responses between family physicians (fps) and specialists.

RESULTS

Of 467 physicians sent surveys, 194 responded (42%), among whom 81 (42%) were specialists and 113 (58%) were fps. Compared with the specialists, the fps were significantly less comfortable with reporting, less likely to consider reporting, less likely to have patients inquire about driving, and less likely to discuss driving implications. A lack of tools, concern for the patient-physician relationship, and a desire to preserve patient quality of life were the most commonly cited barriers in determining medical fitness of patients to drive.

CONCLUSIONS

Legal requirements to report medically unfit drivers put physicians in the difficult position of balancing patient autonomy and public safety. More comprehensive and definitive guidelines would be helpful in assisting physicians with this public health issue.

High peak-power stretcher-free femtosecond fiber amplifier using passive spatio-temporal coherent combining

We report on the passive coherent combining of up to 8 temporally and spatially separated ultrashort pulses amplified in a stretcher-free ytterbium-doped fiber system. An initial femtosecond pulse is split into 4 temporal replicas using divided-pulse amplification, and subsequently divided in two counter-propagating beams in a Sagnac interferometer containing a fiber amplifier. The spatio-temporal distribution of the peak-power inside the amplifier allows the generation of record 3.1 µJ and 50 fs pulses at 1 MHz of repetition rate with 52 MW of peak-power from a stretcher-free fiber amplifier and without additional nonlinear post-compression stages.

Passive coherent combination of two ultrafast rod type fiber chirped pulse amplifiers

Using passive coherent beam combining of two ultrafast fiber amplifiers, we demonstrate the generation of high temporal quality 300 fs and 650 μJ pulses corresponding to 60 W of average power at a repetition rate of 92 kHz. Furthermore, at 2 MHz of repetition rate record coherent combining average powers of 135 W before and 105 W after compression are measured. A combining efficiency higher than 90% is maintained over the whole range of output powers and repetition rates investigated demonstrating the efficiency and robustness of the passive combining technique. The measured pulse-to-pulse relative power fluctuation at high energy is 2%, indicating that the system is essentially immune to environmental phase noise. We believe the passive combining method to be an attractive approach for compact multi-GW peak power femtosecond fiber-based sources.