Prediction of noisy chaotic time series using an optimal radial basis function neural network

This paper considers the problem of optimum prediction of noisy chaotic time series using a basis function neural network, in particular, the radial basis function (RBF) network. In the noiseless environment, predicting a chaotic time series is equivalent to approximating a nonlinear function. The optimal generalization is achieved when the number of hidden units of a RBF predictor approaches infinity. When noise exists, it is shown that an optimal RBF predictor should use a finite number of hidden units. To determine the structure of an optimal RBF predictor, we propose a new technique called the cross-validated subspace method to estimate the optimum number of hidden units. While the subspace technique is used to identify a suitable number of hidden units by detecting the dimension of the subspace spanned by the signal eigenvectors, the cross validation method is applied to prevent the problem of overfitting. The effectiveness of this new method is evaluated using simulated noisy chaotic time series as well as real-life oceanic radar signals. Results show that the proposed method can find the correct number of hidden units of an RBF network for an optimal prediction.

Localization of expression of fibroblast growth-factors and their receptors in pancreatic adenocarcinoma by in-situ hybridization

Growth factors may play a role in autocrine or paracrine growth control of tumour cells. We have now examined the expression pattern in vivo by in situ hybridization (ISH) on a series of 13 ductal adenocarcinomas of the pancreas using the non-radioactive digoxigenin system to generate specific antisense orientated riboprobes for FGF-1 and FGF-2, and the four FGFRs (FGFR-1, -2, -3 and -4). We confirmed the expression of both FGF/FGFR by tumour cells, with the potential of a potential autocrine loops in 46% of the cases studied. FGF-2 and FGFR-3 were the most commonly expressed ligand and receptor (46% and 76% respectively). Endothelial cells lining vessels within an around invasive tumours were frequently positive for expression of FGFR-1 and/or FGFR-3. In the normal pancreas remote from the tumour, the acinar cells were found to have a heterogeneous expression pattern for FGFRs while duct cells, islet cells and stromal components including nerves and vascular endothelium were negative. The data suggest a role for FGFs and their high affinity receptors in the control of growth of human pancreatic adenocarcinoma and its supporting stroma.

Tolerability and efficacy of anti-androgen manipulation versus taxotere and anti-androgen manipulation in patients with hormone-naive, high-risk/metastatic prostate cancer: A phase II, open-labeled, randomized study

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Background: Anti-androgen manipulation (AA) is considered the standard initial therapy for high-risk/metastatic prostate cancer. The role of chemotherapy and anti-androgen manipulation (TAA) is still undefined in this group. GenTax is a phase II trial investigating clinical outcome and gene profiling in prostate cancer before and after AA or TAA. Here we present the clinical outcome data.

Methods: Patients with T3/4 disease, PSA ≥ 50 ng/ml or Gleason score ≥ 8, or metastatic disease were enrolled. Patients were randomised at histological diagnosis to AA or TAA (goserelin 3.6 mgs q28 ± taxotere 75 mg/m2 q21 for 6 cycles). TRUS biopsies were taken at randomisation and 22 weeks after treatment initiation. Clinical assessment including KPS, QOL using QLQ-C30, bloods/PSA were measured 3 weekly until 22 weeks then 3 monthly. Data was analysed for PFS, OS, toxicities and QOL.

Results: 30 patients were recruited with 15 patients in each arm from 10/13/2005 to 12/02/2009. The median age was 62.2 yrs (range 48.9-75.1). All patients had a KPS of ≥ 90%. 12 (40%) and 18 (60%) of patients had stage 3 and 4 disease respectively. At randomization 10 patients had bone and 4 had visceral metastases. 29 had a Gleason score of ≥ 7. There were no statistical differences for age, KPS, disease stage or Gleason score between the two arms. Treatment was well tolerated in both groups with no G3-4 toxicity in the AA arm. In the TAA arm, 4 patients had dose delays or reductions; with one G3 incidence of neutropenia. G3-4 non-hematological toxicities were infrequent; fatigue and one episode of anaphylaxis occurring in separate patients. Median PFS and OS between the two treatments have not been reached at median follow up of 25 months. The 2-year PFS rate was not significantly different, (50% vs 60% p = 0.788) between the AA and TAA groups. There were no significant differences in QOL measures.

Conclusions: Combination therapy of taxotere and anti-androgen manipulation is safe and well tolerated. The gene profiling results may provide important information in selecting patients who will benefit from more aggressive initial therapy.

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An expedited stroke triage pathway: the key to shortening the door-to-needle time in delivery of thrombolysis

OBJECTIVES

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.

DESIGN

Prospective study.

SETTING

A university teaching hospital in Hong Kong.

PATIENTS

Patients with suspected hyperacute stroke referred to the stroke thrombolysis team during October 2008 to September 2009.

MAIN OUTCOME MEASURES

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.

RESULTS

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 patients were 33 (25) and 80 (25) minutes, respectively; both were about 20 minutes longer than that recommended by the National Institute of Neurological Disorders and Stroke. The mean National Institute of Health Stroke Scale score for patients received intravenous recombinant tissue plasminogen activator was 16 (standard deviation, 7). The mean (standard deviation) onset-to-treatment time was 144 (42) minutes. Nine (53%) patients who received intravenous recombinant tissue plasminogen activator achieved favourable outcomes at 3 months, with a modified Rankin Scale score of 0 to 1. Symptomatic haemorrhage and mortality occurred in one (6%) patient.

CONCLUSION

A dedicated stroke triage pathway is essential to ensure efficient and safe delivery of thrombolysis therapy. Improvements in door-to-stroke team time through integration with emergency medicine staff and neuroradiologists may improve thrombolysis eligibility.

Relationship between Phylogeny and Pathotype for the Bacterial Blight Pathogen of Rice

Several transposable elements were isolated from the genome of Xanthomonas oryzae pv. oryzae. These elements and an avirulence gene isolated from X. oryzae pv. oryzae were used as hybridization probes for a collection of X. oryzae pv. oryzae strains from the Philippines. Each of the sequences was present in multiple copies in all strains examined and showed distinct patterns of hybridizing bands. Phenograms were derived from the restriction fragment length polymorphism data obtained for each of the individual probes and for pooled data from multiple probes. The phenograms derived from the different probes differed in topology and, on the basis of bootstrap analysis, were not equally robust. For all of the probes, including the avirulence gene, some groups (even some haplotypes) consisted of multiple races. The strains were grouped into four major clusters on the basis of the two probes giving the highest bootstrap values. These groups were inferred to represent phylogenetic lineages. Three of the six races of X. oryzae pv. oryzae appeared in more than one of the lineages, and another was present in two sublineages. For three of the races, strains representing different phenetic groups were inoculated on rice cultivars carrying 10 resistance genes. Two new races were differentiated, corresponding to pathogen lineages identified by DNA typing. On the basis of DNA and pathotypic analyses, together with information on the spatial and temporal distribution of the pathogen types from this and other studies, a general picture of X. oryzae pv. oryzae evolution in the Philippines is presented.

Reversible Cerebral Vasoconstriction Syndrome with Posterior Leucoencephalopathy after Oral Contraceptive Pills

Reversible cerebral vasoconstriction syndrome (RCVS) is characterized by sudden-onset recurrent ‘thunderclap’ headaches with reversible multifocal narrowing of the cerebral arteries, often associated with focal neurological deficits from ischaemic or haemorrhagic stroke. It has been associated with exposure to vasoconstrictive drugs, pregnancy, migraine, and a variety of other conditions. Whereas the pathophysiology of RCVS remains unclear, changes in the levels of female hormones are considered important because RCVS predominantly affects women and is frequently associated with pregnancy. We report a patient with angiographically confirmed RCVS whose MRI showed reversible brain oedema, suggesting an overlap between RCVS and the reversible posterior leucoencephalopathy syndrome. The only identified risk factor was oral contraceptive pills started 1 month prior to onset, supporting a role for female reproductive hormones in precipitating this overlap syndrome.

Agreement between initial and final diagnosis of first seizures, epilepsy and non-epileptic events: a prospective study

BACKGROUND

Differentiating between first seizure, epilepsy and a non-epileptic event is a challenging clinical exercise for many physicians as it may lead to different therapeutic implications. This study aims to investigate the agreement between the initial diagnosis at the accident and emergency (A&E) department and the final diagnosis following inpatient neurological evaluation of seizure disorders.

METHOD

A prospective observational study between April 2004 and June 2005 in a regional hospital in Hong Kong recruited 1701 patients from the A&E to neurology/medical wards with initial diagnoses/labels matching any one of 12 predefined keywords which were categorised as either "seizure specific" or "non-specific".

RESULTS

Among the 1170 patients with "non-specific" initial diagnoses/labels, 58 (5%) were finally diagnosed as having had a first seizure or epilepsy. Among 531 patients with "seizure specific" initial diagnoses/labels, 27 (5.1%) were subsequently diagnosed as having had non-epileptic events. The kappa value for agreement between the initial and final diagnosis was 0.88. Of the 154 patients with a final diagnosis of first seizure, 34 (22%) had "non-specific" initial labels. Among these patients, components of the evaluation contributing to revision of diagnosis included retrieval of witness accounts (47%), epileptiform discharges on EEG (47%), short term monitoring in patients suspected of acute symptomatic seizures (28%) and panel discussion of cases (22%).

CONCLUSION

There was generally a high degree of agreement between the initial and final diagnosis, but first seizures were often missed initially. Careful history taking, judicious use of EEG, selective short term monitoring and liaison with specialists are important in reaching an accurate diagnosis.

Finding the missing link between ictal bradyarrhythmia, ictal asystole, and sudden unexpected death in epilepsy

Basic science studies of the human brain have supported the cortical representation of cardiovascular responses, including heart rate variability. Clinical observations of ictal bradyarrhythmia may be mechanistically explained by the influence of the central autonomic network, although the localization and lateralization issues need to be considered in the light of patterns of seizure spread, hand dominance, and presence of lesions. Ictal bradyarrhythmia also offers a mechanistic explanation of sudden unexpected death in epilepsy (SUDEP), though it may explain only some but not all cases of SUDEP. The missing links are (1) clinical evidence of common factors shared by patients with ictal bradyarrhythmia and patients who die from SUDEP, (2) evidence of arrhythmia as a risk factor for SUDEP from epidemiological studies, and, (3) determination of the importance of ictal bradyarrhythmia in SUDEP with respect to other proposed mechanisms including apnea and intrinsic cardiac abnormalities. There remains a need to review the seizure mechanisms in cases of SUDEP and to step up the amount of concurrent ECG/intracranial EEG analysis in both ictal bradyarrhythmia and SUDEP cases.

Dyslipidaemia and microvascular disease in the retina

PURPOSE

There are few data on the effect of serum lipids on microvascular disease. This study assessed the relationships between serum lipid levels and microvascular disease, as seen in the retina, among participants who attended a population-based study in Australia (n=3654, aged 49+years).

METHODS

Diameters of retinal arterioles and venules were measured from digitised photographs of each participant to obtain an estimate of generalised arteriolar narrowing. Focal arteriolar narrowing, arteriovenous nicking, and retinopathy lesions (microaneurysms, haemorrhages, hard/soft exudates) were graded using a standard protocol. Fasting blood tests were performed in 89% of subjects. Adjusted means were calculated using general linear models. Logistic regression models were used to determine the odds ratios for retinal microvascular signs.

RESULTS

After controlling for age, sex, body mass index, smoking, and mean arterial blood pressure, elevated high-density lipoprotein cholesterol was associated with narrower retinal arterioles (Ptrend=0.002) and venules (Ptrend=0.03) and with increased odds of generalised arteriolar narrowing (odds ratio 1.6, 95% confidence interval 1.1-2.2 for the highest vs the lowest quintile of high-density lipoprotein cholesterol). Serum triglyceride had a U-shaped relationship with venular diameter (Ptrend=0.003). We found no consistent pattern of association between serum total cholesterol or low-density lipoprotein cholesterol and any retinal microvascular signs.

CONCLUSIONS

These findings suggest that microvascular disease in the retina may result from processes distinct from dyslipidaemia.

Parkinson's disease: aetiology, diagnosis, and management

OBJECTIVE

To review the aetiology, diagnosis, and management of Parkinson's disease, with a local perspective.

DATA SOURCES

Medline from 1966 onwards, and all major neurological journals and movement disorder journals were searched for evidence on the aetiology, diagnosis, and management of Parkinson's disease.

STUDY SELECTION

Key words for the literature search were "Parkinson's disease" and "Chinese" or "Hong Kong".

DATA EXTRACTION

All relevant articles in English were reviewed.

DATA SYNTHESIS

The number of promising genes for familial Parkinson's disease is still expanding rapidly and there has been a wealth of studies on susceptibility genes for Parkinson's disease. Potential treatment choices include the use of agents thought to be neuroprotective, symptomatic treatment with drugs or surgery, and non-pharmacological treatments. Pharmacological treatment using a dopa-sparing strategy and continuous dopaminergic stimulation is now gaining support to address the issue of long-term motor complications. Surgical treatment with deep brain stimulation is safe and effective for refractory cases and has been increasingly utilised locally.

CONCLUSIONS

Medical therapy remains the mainstay of treatment and newer agents and treatment approaches are emerging, which will hopefully address the issue of neuroprotection and provide symptomatic treatment with fewer motor complications.