DualSort: online spike sorting with a running neural network

Objective.Spike sorting, i.e. the detection and separation of measured action potentials from different extracellularly recorded neurons, remains one of the bottlenecks in deciphering the brain. In recent years, the application of neural networks (NNs) for spike sorting has garnered significant attention. Most methods focus on specific sub-problems within the conventional spike sorting pipeline, such as spike detection or feature extraction, and attempt to solve them with complex network architectures. This paper presents DualSort, a simple NN that gets combined with downstream post-processing for real-time spike sorting. It shows high efficiency, low complexity, and requires a comparatively small amount of human interaction.Approach.Synthetic and experimentally obtained extracellular single-channel recordings were utilized to train and evaluate the proposed NN. For training, spike waveforms were labeled with respect to their associated neuron and position in the signal, allowing the detection and categorization of spikes in unison. DualSort classifies a single spike multiple times in succession, as it runs over the signal in a step-by-step manner and uses a post-processing algorithm that transmits the network output into spike trains. Main results.With the used datasets, DualSort was able to detect and distinguish different spike waveforms and separate them from background activity. The post-processing algorithm significantly strengthened the overall performance of the model, making the system more robust as a whole. Although DualSort is an end-to-end solution that efficiently transforms filtered signals into spike trains, it competes with contemporary state-of-the-art technologies that exclusively target single sub-problems in the conventional spike sorting pipeline.Significance.This work demonstrates that even under high noise levels, complex NNs are not necessary by any means to achieve high performance in spike detection and sorting. The utilization of data augmentation on a limited quantity of spikes could substantially decrease hand-labeling compared to other studies. Furthermore, the proposed framework can be utilized without human interaction when combined with an unsupervised technique that provides pseudo labels for DualSort. Due to the low complexity of our network, it works efficiently and enables real-time processing on basic hardware. The proposed approach is not limited to spike sorting, as it may also be used to process different signals, such as electroencephalogram (EEG), which needs to be investigated in future research.

The impact of intraoperative goal-directed fluid therapy on complications after pancreaticoduodenectomy

INTRODUCTION

Optimal fluid balance is critical to minimize anastomotic edema in patients undergoing pancreaticoduodenectomy. We examined the effects of decreased fluid administration on rates of postoperative pancreatic leak and delayed gastric emptying.

METHODS

Retrospective study of 105 patients undergoing pancreaticoduodenectomy at a single institution from January 2015 through July 2016. Stroke volume variation (SVV) was tracked and titrated during the procedure. A comparative analysis of postoperative complications was performed between patients with a median SVV < 12 during the extirpative and reconstructive phases of the procedure compared with patients with an SVV ≥ 12.

RESULTS

Of 64 patients who met selection criteria, 42 (65.6%) had a SVV < 12 and 22 (34.4%) had a SVV ≥ 12. Patients with an SVV ≥ 12 during the extirpative phase of the procedure had lower rates of postoperative pancreatic leaks compared to patients with an SVV < 12 (5.9% vs 21.3%)). Patients with an SVV ≥ 12 during the extirpative phase had lower rates of postoperative delayed gastric emptying compared to patients with an SVV < 12 (41.2% vs 46.8%).

CONCLUSION

Goal-directed fluid restriction before the reconstructive phase of pancreaticoduodenectomy may contribute to lower postoperative rates of pancreatic leak and delayed gastric emptying.

[Predictability of residual astigmatism after implantation of posterior chamber toric lenses]

BACKGROUND

The objective of the study was to examine the predictability of residual astigmatism after cataract surgery and implantation of the posterior chamber aspheric toric lens TECNIS® ZCT, Abott Medical Optic (Ettlingen, Deutschland).

MATERIAL AND METHODS

The retrospective study included a total of 88 patient eyes undergoing a cataract operation with a toric lens implantation between March 2014 and October 2015. The inclusion criteria were a regular astigmatism of at least 0.75 dpt. Posterior chamber toric lenses (model Tecnis ZCT) were exclusively implanted. Post-surgery check-ups were performed after 1 day, 1 month and 2 months. Main study outcome was best-corrected visual acuity (BCVA), spherical and astigmatic aberration and the difference between expected and actual residual astigmatism after cataract surgery.

RESULTS

The median reduction of corneal astigmatism was from -2.50 dpt (±1.06 dpt) to -0.75 dpt (±0.51 dpt) (p ≤ 0.05). The median BCVA increased from 0.37 logMAR (±0.25 logMAR) before surgery to 0.09 logMAR (±0.10 logMAR) after surgery. The spherical equivalent was reduced from +3.50 dpt (±1.11 dpt) (presurgery) to -0.56 dpt (±0.51 dpt) (postsurgery) in hyperopic patients and from -2.44 dpt (±3.03 dpt) to -0.69 dpt (±0.81 dpt) in myopic patients. By using the power vector analysis no significant deviation from the expected target values was observed; however, the median discrepancy between the expected and actual residual astigmatism was -0.50 dpt despite a surgical orientation of the intraocular lens (IOL) within 5° of the desired axis. The IOL showed a median rotation of 3.00° (±4.46°).

CONCLUSION

Implantation of the aspheric toric intraocular lens Tecnis ZCT is a predictable, effective and reproducible tool in cataract surgery to account for regular corneal astigmatis; however, despite an optimal surgical orientation of the toric IOL, a small and rarely a large discrepancy might occur between expected and actual residual astigmatism.

The role of wealth in the experience of quality of life of the semi–affluent investor

In an attempt to assist semi-affluent investors’ best use their wealth to improve their lives, this study explores the role of wealth in the experience of quality of life. Seven clients of a financial advisory firm based in the U.S.A, were interviewed using the repertory grid technique. Through an interpretive analysis wealth was found to influence the experience of quality of life in the way that it was used to satisfy individual material and security needs; shape growth and relatedness needs and influence how respondents establish, maintain and verify their identity.

Delayed postpartum hemorrhage: a rare presentation of carbon monoxide poisoning

A 41-year-old woman presented with postpartum hemorrhage and altered mentation. A markedly elevated serum carboxyhemoglobin level was noted. Oxygen therapy was initiated with resolution of the patient's bleeding and improved mental status. Carbon monoxide poisoning is a rare and previously unreported cause of postpartum hemorrhage resulting from a unique pathophysiologic mechanism.

Circular Dichroism and NMR Studies of Metabolically Stableα-Methylpolyamines: Spectral Comparison with Naturally Occurring Polyamines

Three synthetic polyamine analogs, alpha-methylspermine, and alpha,alpha'-dimethylspermine, were compared with their naturally occurring counterparts, spermidine and spermine, by two different spectral techniques. The interaction of polyamines with oligodeoxynucleotides was measured by circular dichroism in order to monitor the polyamine-induced conversion of right-handed B-DNA to the left-handed Z-form. The methylated analogs were shown to be equally effective as the natural polyamines in inducing the B --> Z transition. The pH dependence of the chemical shift of all carbon atoms in each of the five polyamines was measured by (13)C-NMR spectroscopy. With the exception of expected changes in chemical shift due to the presence of the alpha-methyl substituents, the chemical shifts and pH dependence of all carbon atoms in the three alpha-methyl polyamines were similar to the corresponding naturally occurring polyamines. The combined data indicate that alpha-methyl polyamines have physical properties that are very similar to their natural counterparts. The two metabolically stable polyamine analogs, alpha-methylspermidine and alpha,alpha'-dimethylspermine, are therefore useful surrogates for spermidine and spermine in the study of numerous polyamine-mediated effects in mammalian cell cultures and can be used in such studies without the requirement for coadministration of amine oxidase inhibitors.

Ventricular remodeling during development and recovery from modified tachycardia-induced cardiomyopathy model

This study was designed to characterize left ventricular (LV) function and mass in a modified cardiomyopathy model in the dog in which right ventricular pacing rates are gradually increased throughout 38 days. On the last day of the pacing protocol, ejection fraction was reduced (25 +/- 3 vs. 60 +/- 1%) and LV end-diastolic diameter index (a ratio of LV end-diastolic diameter to body weight, 2.09 +/- 0.02 vs. 1.79 +/- 0.08 mm/kg) and LV mass index (a ratio of LV mass to body weight, 5.2 +/- 0.3 vs. 4.3 +/- 0.2 g/kg) were greater than in the normal dogs (P < 0.05, respectively). Cardiac filling pressures increased, and LV diastolic function and coronary blood flow were impaired. After 4 wk of recovery from the progressive pacing protocol, LV end-diastolic diameter index (2.12 +/- 0.06 mm/kg) and LV mass index (5.6 +/- 0.2 g/kg) remained increased. Ejection fraction was improved (38 +/- 4%) but still depressed. LV diastolic function, coronary blood flow, and cardiac filling pressures returned to levels seen in the normal dogs. This modified cardiomyopathy model associated with LV hypertrophy complements the conventional tachycardia-induced cardiomyopathy model without LV hypertrophy.

Verrucous cyst

Human papillomavirus has been detected in a variety of cutaneous premalignant and malignant conditions, as well as in benign cutaneous warts. Changes consistent with epidermis papilloma virus infection occurring in epidermal cysts have recently been reported in the dermatologic literature only in plantar epidermal cysts. We report five examples of a form of cutaneous cyst that is histologically distinctive and that has not been previously reported, to our knowledge. We describe five cases of epidermal cysts showing marked verrucous changes of their stratified squamous inner linings, some of which also show proliferative changes. Human papillomavirus genomes were detected via polymerase chain reaction. None of the DNA probes for Southern blot hybridization demonstrated homology with the human papillomavirus types usually associated with cutaneous warts or carcinoma. We believe this cyst to represent a newly described manifestation of human papillomavirus infection, and propose the name verrucous cyst for this entity. Further studies may reveal the specific human papillomavirus type(s) associated with the verrucous cyst.

Screening for sickle cell trait: the Veterans Administration National Sickle Cell Program

Results of the Veterans Administration Sickle Cell Program for a period of 10 years are presented. We screened 370,250 patients; 404,341 attended educational sessions, and 38,347 had individual counseling sessions. Sickle cell trait was present in 6.4% of patients, and HbC trait was present in 1.8%. The clinically significant disorders HbSC disease, sickle cell anemia, and sickle beta thalassemia were present in 0.41% of individuals screened. A large number of uncommon variants were detected. The program enhanced the awareness of and the approach to evaluation of hemoglobinopathies.

Small nuclear RNA U2 is base-paired to heterogeneous nuclear RNA

Eukaryotic cells contain a set of low molecular weight nuclear RNA's. One of the more abundant of these is termed U2 RNA. The possibility that U2 RNA is hydrogen-bonded to complementary sequences in other nuclear RNA's was investigated. Cultured human (HeLa) cells were treated with a psoralen derivative that cross-links RNA chains that are base-paired with one another. High molecular weight heterogeneous nuclear RNA was isolated under denaturing conditions, and the psoralen cross-links were reversed. Electrophoresis of the released RNA and hybridization with a human cloned U2 DNA probe revealed that U2 is hydrogen-bonded to complementary sequences in heterogeneous nuclear RNA in vivo. In contrast, U2 RNA is not base-paired with nucleolar RNA, which contains the precursors of ribosomal RNA. The results suggest that U2 RNA participates in messenger RNA processing in the nucleus.

An improved microchromatographic procedure for separating HbA2 from HbS for the purpose of quantitation

A microchromatographic method for separating hemoglobin A2 from hemoglobin S and their subsequent quantitation on DEAE-cellulose has been improved. The new procedure is more versatile, since the same system can be used when hemoglobin S is present or absent in the sample without changing to a longer column or another buffer system. Also, the technic is less sensitive to small changes in pH of buffers or resin than are other procedures.

Comparison of biochemical properties of human serum B12 binders derived from sephadex and DEAE-cellulose chromatography

Vitamin B12 binding proteins were separated into 2 peaks corresponding to small (TCS) and large (TCL) molecular weight fractions by gel-filtration of Sephadex G-200 using 0.005 M-sodium phosphate buffer, pH 7.4 containing 1 M-NaC1. Each peak, after dialysis and concentration, was chromatographed on DEAE-cellulose. 3 peaks of radioactivity were recovered from both TCS and TCL. Peaks from TCS had an apparent mol. wt. of about 40,000 and those from TCL about 110,000, as determined by gel-filtration on Sephadex G-200. On electrophoresis, peaks eluted with 0.06 M-phosphate buffer, pH 5.85 from both TCS and TCL moved as beta-globulins; those eluted with 0.1 M buffer, pH 5.8 between beta- and alpha 2-globulin and those eluted with 0.25 M buffer, pH 5.4 between alpha 1-globulin. In our assay system, TCS delivered 57CoB12 to L-1210 leukaemic lymphoblasts while TCL had no such activity. Of the 6 binders from DEAE-cellulose, only peaks eluted with 0.06 M and 0.1 M buffers from TCS delivered labelled B12 to these cells. Antisera prepared against TC II B12 reacted only with TC II B12 from serum, TCS, and fractions D and E obtained from TCS which were eluted with 0.06 and 0.1 M buffers, respectively.

Malignant Lymphoma (So-Called Leukemia) in Dogs

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