Evaluation of colposuspension for treatment of incontinence in spayed female dogs.

OBJECTIVE: To determine the long-term effects of colposuspension in spayed female dogs with urinary incontinence and identify preoperative anatomic or urodynamic measurements associated with a successful outcome. DESIGN: Prospective study. ANIMALS: 23 client-owned spayed female dogs with urinary incontinence. PROCEDURE: Prior to surgery, a history was obtained, and a physical examination, CBC, serum biochemical analyses, urinalysis, bacterial culture of a urine sample, vaginourethrocystography, urethral pressure profilometry, and leak point pressure test were performed. Colposuspension was performed, and preoperative tests were repeated 2 months after surgery. Clients were interviewed 2 weeks, 1 month, and 1 year after surgery. RESULTS: 22 dogs were followed up for 1 year. Twelve had complete urinary control 2 months after surgery, and 3 had complete urinary control 1 year after surgery. Dogs with normal urinary control at 2 months had an increased leak point pressure (LPP), compared with preoperative measurements, and their LPP was the same as normal dogs. Eight dogs had complete urinary control, and 9 were considered greatly improved 1 year after surgery when medical treatment was added to the effect of colposuspension. Client satisfaction was high, with 19 of 22 (86%) owners being pleased with their decision to have surgery performed. The only predictors of complete urinary control 2 months after surgery were a more caudal position of the external urethral opening in relation to the pubis on preoperative radiographs and a longer overall urethral length. CONCLUSIONS AND CLINICAL RELEVANCE: Colposuspension alone will result in complete urinary control in few dogs with urinary incontinence but may improve urinary control sufficiently that owners will be pleased. Preoperative vaginourethrocystography may be helpful in predicting response to surgery, and the LPP test correlates with improved urinary control.

A rapid and strong laparoscopic-assisted gastropexy in dogs.

OBJECTIVE: To develop a technique for laparoscopic gastropexy in dogs and evaluate effects on stomach position and strength of the adhesion between the stomach and abdominal wall. ANIMALS: 8 healthy dogs. PROCEDURE: Dogs were anesthetized, and the abdomen was insufflated with carbon dioxide. A laparoscope was placed through a cannula inserted on the abdominal midline caudal to the umbilicus. Babcock forceps placed through a cannula inserted lateral to the right margin of the rectus abdominus muscle were used to exteriorize the pyloric antrum, a longitudinal incision was made through the serosa and muscular layer of the pyloric antrum, and the seromuscular layer of the pyloric antrum was sutured to the transversus abdominus muscle. After surgery, positive-contrast gastrography was used to evaluate stomach position and the onset of gastric emptying, and ultrasonography was used to assess stomach wall activity and mobility. Dogs were euthanatized 1 month after surgery, and tensile strength of the adhesion was tested. RESULTS: In all dogs, stomach position and the onset of gastric emptying were normal 25 days after surgery, and the pyloric antrum was firmly attached to the abdominal wall 30 days after surgery. Mean +/- SD ultimate load of the adhesion in tension was 106.5 +/- 45.6 N. CONCLUSIONS AND CLINICAL RELEVANCE: The laparoscopic gastropexy technique described in the present study could be performed quickly and easily by an experienced surgeon, resulted in a strong fibrous adhesion between the stomach and abdominal wall, and appeared to cause minimal stress to the dogs.

A direct brain interface based on event-related potentials.

Cross-correlation between a trigger-averaged event-related potential (ERP) template and continuous electrocorticogram was used to detect movement-related ERP's. The accuracy of ERP detection for the five best subjects (of 17 studied), had hit percentages >90% and false positive percentages <10%. These cases were considered appropriate for operation of a direct brain interface.

Identification of electrocorticogram patterns as the basis for a direct brain interface.

This study reports on the first step in the development of a direct brain interface based on the identification of event-related potentials (ERPs) from an electrocorticogram obtained from the surface of the cortex. Ten epilepsy surgery patients, undergoing monitoring with subdural electrode strips and grid arrays, participated in this study. Electrocorticograms were continuously recorded while subjects performed multiple repetitions for each of several motor actions. ERP templates were identified from action-triggered electrocorticogram averages using an amplitude criterion. At least one ERP template was identified for all 10 subjects and in 56% of all electrode-recording sets resulting from a subject performing an action. These results were obtained with electrodes placed solely for clinical purposes and not for research needs. Eighty-two percent of the identified ERPs began before the trigger, indicating the presence of premovement ERP components. The regions yielding the highest probability of valid ERP identification were the sensorimotor cortex (precentral and postcentral gyri) and anterior frontal lobe, although a number were recorded from other areas as well. The recording locations for multiple ERPs arising from the performance of a specific action were usually found on close-by electrodes. ERPs associated with different actions were occasionally identified from the same recording site but often had noticeably different characteristics. The results of this study support the use of ERPs recorded from the cortical surface as a basis for a direct brain interface.

Detection of event-related potentials for development of a direct brain interface.

The study presented here is part of an ongoing effort to develop a direct brain interface based on detection of event-related potentials (ERPs). In a study presented in a companion article, averaged ERP templates were identified from electrocorticograms recorded during repetition of voluntary motor actions. Here the authors report on the detection of individual motor ERPs within the electrocorticogram using cross-correlation. An averaged ERP template was created from the first half of each electrocorticogram and then cross-correlated with the continuous electrocorticogram from the second half. Points where the cross-correlation value exceeded an experimentally determined detection threshold were considered to be detection points. A detection point was considered to be a valid "hit" if it occurred between 1 second before and 0.25 second after the recorded time of a voluntary action. The difference between the hit and false-positive percentages (HF-difference) was used as a metric of detection accuracy. HF-differences greater than 90 were found for 5 of 15 subjects, HF-differences greater than 75 were found for 8 of 15 subjects, and HF-differences greater than 50 were found for 12 of 15 subjects. The three other subjects with HF-differences less than 50 had electrode locations not well suited for recording movement-related ERPs. Recordings from sensorimotor and supplementary motor areas produced the highest yield of channels with HF-difference greater than 50; however, a number of channels with good performance were found in other areas as well. The results demonstrate the likely prospect of using ERP detection as the basis of a single-switch direct brain interface and that furthermore, there is a good possibility of obtaining multiple control channels using this approach.

ECG boy: low-cost medical instrumentation using mass-produced, hand-held entertainment computers. A preliminary report.

A prototype low-cost, portable ECG monitor, the "ECG Boy," is described. A mass produced hand-held video game platform is the basis for a complete three-lead, driven right-leg electrocardiogram (ECG). The ECG circuitry is planned to fit in a standard modular cartridge that is inserted in a production Nintendo "Gameboy." The combination is slightly smaller than a paperback book and weighs less than 500 g. The unit contains essential safety features such as optical isolation and is powered by 9-V and AA batteries. Functionally, the ECG Boy permits viewing ECG recordings in real time on the integrated screen. The user can select both the lead displayed on the screen and the time scale used. A 1-mV reference allows for calibration. Other ECG enhancements such as data transmission via telephone can be easily and inexpensively added to this system. The ECG Boy is intended as a proof of concept for a new class of low-cost biomedical instruments. Rising health care costs coupled with tightened funding have created an acute demand for low-cost medical equipment that satisfies safety and quality standards. A mass-produced microprocessor-based platform designed for the entertainment market can keep costs low while providing a functional basis for a biomedical instrument.

Measurement of Microscale Patchiness in a Turbulent Aquatic Odor Plume Using a Semiconductor-Based Microprobe.

The distribution of chemical signals within aquatic environments is highly patchy and heterogeneous due to dispersion by turbulent eddies. We aimed to quantify the smallest spatial scales associated with chemical patches, and therefore measured the structure of chemical signals under turbulent flow simultaneously at two chemical sensors spaced from 200 to 800 {mu}m apart. Measurements were done under controlled stimulus and flow conditions with a novel semiconductor-based, multisite, microelectrochemical electrode (5-2000 {mu}m2 surface area sensors) and a high-speed computer-based recording system. The chemical signals received at the sensor were intermittent, with wide fluctuations in concentration. Patchiness in signal structure was found at spatial scales as small as 200 {mu}m. Significant differences in signal height were found between recordings made at probes spaced 200, 400, 600, and 800 {mu}m apart. These data demonstrate that sub-millimeter patches occur in aquatic turbulent odor plumes. Such differences in chemical signal structure over small spatial scales might be important for marine animals that employ olfactory orientation. We propose alternative ways by which organisms might deal with these fine scale differences in odor concentration. Animals much larger than microscale patches may have evolved elongated olfactory organs that integrate signals, thereby smoothing variations in sensory input. Animals about the same size as micropatches may be able to capitalize on microscale variation by extracting directional information from turbulent odor plumes.

Multichannel semiconductor-based electrodes for in vivo electrochemical and electrophysiological studies in rat CNS.

Five-channel silicon-based microprobes were sputter-coated with carbon, coated with Nafion, and used for both in vivo electrochemical and single-unit electrophysiological recordings. High-speed electrochemical studies were performed in vitro and in vivo, which demonstrated that these multisite probes were capable of monitoring the evoked overflow of monoamines in selected brain regions of the rat. In addition, action potentials from Purkinje cells in the rat cerebellum, identified electrophysiologically, were recorded from different sites on the same probe. Spontaneous firing rates could be monitored for up to 2 hours in order to investigate the effects of systemic administration of phencyclidine. These results provide preliminary evidence that solid-state multi-site probes can be utilized for both in vivo electrochemical and electrophysiological studies in the rat brain.

Field-potential evidence for extrasynaptic alterations in the hippocampal CA1 pyramidal cell population during paired-pulse potentiation.

The mechanisms of paired-pulse potentiation of the CA1 pyramidal cell population were examined by determining input-output relations for control and potentiated responses originating from the activation of radiatum fibers in the hippocampal slice preparation. Two types of potentiation for synchronously discharging pyramidal cells (population spike) were observed. In the first type, the potentiation of the population spike was found to be a combination of synaptic and extrasynaptic factors. This form of potentiation was observed in 16 of 28 slices. In the second type, the potentiation of the population spike was attributed entirely to the potentiation of summated dendritic depolarizations (population EPSP). This synaptic process of potentiation was observed in 12 of 28 slices. The involvement of only extrasynaptic mechanisms in the paired-pulse potentiation of the population spike was not observed. For the potentiation originating from a combination of synaptic and extrasynaptic mechanisms, 60% of the potentiation of the population spike was a result of synaptic factors and 40% could be attributed to extrasynaptic factors. These results support the concept that alterations in the excitability of postsynaptic neurons serve as a component of the mechanisms of paired-pulse potentiation in the radiatum fiber-CA1 pyramidal cell system.

Periodic fluctations in synaptic transmission and enhancement of transmission in hippocampal slices.

The properties of the synchronously activated radiatum fiber-CA1 synaptic population were examined with the in vitro hippocampal slice preparation. Periodic fluctuations in synaptic transmission and in the enhancement of synaptic transmission were observed with periods ranging from 8 to 20 s. Such periodic fluctuations did not arise from fluctuations in afferent radiatum fiber activity. The period and amplitude of the cyclic variations in the enhancement of synaptic transmission were found to be altered with repeated electrical stimulation of the radiatum fibers. These results reflect cooperative synaptic actions which must be taken into consideration in the delineation of the mechanisms of potentiation.

Compound action potential reconstructions and predicted fiber diameter distributions.

Electrophysiologic and anatomic studies on cat saphenous nerve were combined with CAP modelling and computer analysis. Myelinated nerve FD histograms were compiled from transverse section photomicrographs using various estimates of diameter, primarily those based on fiber cross-section area. The FD histogram and biophysical parameters were more important in the CAP reconstruction model than the SFAP parameters. The biophysical parameters were optimized to obtain best fits between recorded and reconstructed CAPs. Finally, the inverse of the CAP reconstruction model was used to predict FD histograms from optimized biophysical parameters and recorded CAP waveforms under carefully controlled experimental conditions. The results of these studies provide an empirical basis for relating volume conducted CAPs to the anatomic and physiologic characteristics of nerve fiber bundles. More accurate histologic methods and procedures for estimating biophysical parameters are needed before this approach to the inverse problem can be pursued further. The major advantage of estimating FD distributions rather than CV distributions is that the anatomic data are truly independent reference standards for evaluating the results.