Efficient neural spike sorting using data subdivision and unification.

Neural spike sorting is prerequisite to deciphering useful information from electrophysiological data recorded from the brain, in vitro and/or in vivo. Significant advancements in nanotechnology and nanofabrication has enabled neuroscientists and engineers to capture the electrophysiological activities of the brain at very high resolution, data rate and fidelity. However, the evolution in spike sorting algorithms to deal with the aforementioned technological advancement and capability to quantify higher density data sets is somewhat limited. Both supervised and unsupervised clustering algorithms do perform well when the data to quantify is small, however, their efficiency degrades with the increase in the data size in terms of processing time and quality of spike clusters being formed. This makes neural spike sorting an inefficient process to deal with large and dense electrophysiological data recorded from brain. The presented work aims to address this challenge by providing a novel data pre-processing framework, which can enhance the efficiency of the conventional spike sorting algorithms significantly. The proposed framework is validated by applying on ten widely used algorithms and six large feature sets. Feature sets are calculated by employing PCA and Haar wavelet features on three widely adopted large electrophysiological datasets for consistency during the clustering process. A MATLAB software of the proposed mechanism is also developed and provided to assist the researchers, active in this domain.

Compatibility Evaluation of Clustering Algorithms for Contemporary Extracellular Neural Spike Sorting.

Deciphering useful information from electrophysiological data recorded from the brain, in-vivo or in-vitro, is dependent on the capability to analyse spike patterns efficiently and accurately. The spike analysis mechanisms are heavily reliant on the clustering algorithms that enable separation of spike trends based on their spatio-temporal behaviors. Literature review report several clustering algorithms over decades focused on different applications. Although spike analysis algorithms employ only a small subset of clustering algorithms, however, not much work has been reported on the compliance and suitability of such clustering algorithms for spike analysis. In our study, we have attempted to comment on the suitability of available clustering algorithms and performance capacity when exposed to spike analysis. In this regard, the study reports a compatibility evaluation on algorithms previously employed in spike sorting as well as the algorithms yet to be investigated for application in sorting neural spikes. The performance of the algorithms is compared in terms of their accuracy, confusion matrix and accepted validation indices. Three data sets comprising of easy, difficult, and real spike similarity with known ground-truth are chosen for assessment, ensuring a uniform testbed. The procedure also employs two feature-sets, principal component analysis and wavelets. The report also presents a statistical score scheme to evaluate the performance individually and overall. The open nature of the data sets, the clustering algorithms and the evaluation criteria make the proposed evaluation framework widely accessible to the research community. We believe that the study presents a reference guide for emerging neuroscientists to select the most suitable algorithms for their spike analysis requirements.

Aerobic vaginal pathogens and their sensitivity pattern.

BACKGROUND: The vaginal flora is a complicated environment, containing dozens of microbiological species in variable quantities and relative proportions. The frequent cause of vaginal discharge is an infection or colonization with different microorganisms. Some pathologic conditions causing vaginitis are well defined yet, 7-72% of women with vaginitis may remain undiagnosed and such forms of abnormal vaginal flora neither considered as normal, nor can be called bacterial vaginosis have been termed as 'intermediate flora' and its management probably differ from that of bacterial vaginosis. It is of crucial importance in pregnant females at risk of preterm delivery. The present study has been conducted especially to elucidate this type of aerobic vaginal isolates and their culture and sensitivity towards currently used antibiotics. This study was conducted at the Microbiology Department of Fauji Foundation Hospital, Rawalpindi over a period of two years (April 2004-March 2006). METHODS: One thousand, nine hundred and twenty three high vaginal swabs, both from indoor and outdoor patients were collected, cultured and their susceptibility to various antibiotics was determined. RESULTS: Significant growth was obtained in 731 samples. The highest frequency of infection (39.5%) was observed at 31-40 years followed by 41-50 years (35.8%). About 76% were from outdoor and 24% were from indoor patients. Staphylococcus aureus was the most prevalent vaginal pathogen at 11-60 yrs & with highest prevalence at 31-40 years followed by 41-50 years. It was a predominant pathogen in both indoor (35%) as well as outdoor (41.6%) patients, followed by enteric gram-negative bacilli and other gram-positive cocci. There were very few antibiotics among the conventionally available aminoglycosides, third generation cephalosporins, penicillin, quinolones, sulfonamides and tetracyclines possessing good sensitivity (> 80%) against any one the common aerobic vaginal pathogens. The effective chemotherapeutics agents belong to the groups of carbapenems and beta-lactams beta-lactamase inhibitor combinations. CONCLUSIONS: The high prevalence of gynaecological infections demands that the patients with gynaecological symptoms be investigated thoroughly. Culture must invariably be done. Currently the antibiotics showing good sensitivity are very expensive. So there is a need for an effective antimicrobial policy. Effective drug should be reserved for the treatment of serious life threatening situations only.

Extended spectrum beta-lactamases in enteric gram-negative bacilli: related to age and gender.

BACKGROUND: Extended Spectrum beta-Lactamases (ESBLs)-producing strains of Enterobacteriaceae have emerged as a major problem in hospitalized as well as community based patients. Infections due to ESBLs-producers range from uncomplicated urinary tract infection to life threatening sepsis. The objective of this study was to find out the prevalence of ESBLs-producing Gram- negative bacilli among clinical isolates. METHODS: This descriptive study was conducted at the Microbiology department of Fauji Foundation Hospital, Rawalpindi over a period of two years (March 2004-April 2006). Six hundred and nine isolates of Enteric Gram-negative rods from various samples were tested for ESBLs-production by double disc synergy test. In 176 ESBLs-producing isolates, source of samples in term of indoor/outdoor was analyzed. In 165 ESBLs-producing isolates, patients' gender and age was analysed from 3 months to 70 years. RESULTS: The ESBLs-producing isolates were more commonly isolated from indoor patients (88.1%) as compared to outdoor patients (11.9%). Escherichia coli was found to be most prevalent organism in indoor patients while Klebsiella pneumoniae, was the most prevalent organism in outdoor patients. ESBLs were most commonly isolated from female patients (64.3%) suffering from urinary tract infections ((41.5%), as compared to male patients (35.7%) in which the organisms were most commonly isolated from pus samples (54.2 %). ESBLs-producing Enteric Gram-Negative rods were most frequent at later part of life where they were most common (27.9%) at 61-70 years, followed by 41-50 years of age group (20.0%). Another peak (13.3%) was also seen at younger age group (11-20 years). The least prevalence (5.5%) was seen in two age groups (0-10 and 31-40 yrs). In case of female patients, ESBLs-producing EGNR were most frequently (29.2%) isolated from middle age group (41-50 years) followed by later age groups (51-60 and 61-70 years, (15.1% and 25.5%). CONCLUSIONS: Considering the high prevalence of ESBLs in Enteric Gram-negative rods, it is suggested that all such isolates should be tested for the production of ESBLs in the routine microbiology laboratory.

(99m)Tc Diethylenetriaminepentacetic Acid Angiotension-coverting Enzyme Inhibitor Renography as Screening Test for Renovascular Hypertension in Unilateral Small Kidney: A Prospective Study.

To know the probability of renal artery stenosis (RAS) in unilateral small kidney and function of the unilateral small kidney, which includes glomerular filtration rate, differential function, uptake, Tmax by (99m)Tc diethylenetriaminepentacetic acid (DTPA) base and (99m)Tc DTPA angiotensin converting enzyme (ACE) inhibition scan. All our patients were subjected to (99m)Tc DTPA ACE inhibition renal scintigraphy. All the patients underwent either computed tomography (CT) angiography and magnetic resonance (MR) angiography was done in those patients in which kidney function test was deranged. Renal angiography was subsequently performed in cases with the suggestion of RAS on CT or MR angiography. The quantitative data was expressed as the arithmetic mean, standard deviation and percentages. The intergroup comparisons for parametric data were done by Student's t-test, whereas non-parametric data was compared with Mann-Whitney U-test. The intergroup comparisons were made by paired t-test and Wilcoxon sign rank test. P <0.05 was considered to be significant, and data was analyzed by Statistical package for social sciences(SPSS-20) software. Out of 47 patients, 25 patients were in the low probability group out of which none was positive for RAS on CT/MR angiography. Out of 47 patients, 12 were in the intermediate group out of which none was positive for RAS. Ten, out of 47 patients were suspected of high probability for RAS by ACE inhibition scan out of which 4 were positive for RAS by CT/MR angiography including one with bilateral RAS. (99m)Tc DTPA angiotension-coverting enzyme inhibitor renography is a safe, non-invasive, sensitive, specific, and cost-effective test for excluding renovascular hypertension in patients who have normal or nearly normal renal function in unilateral small kidney.