Emersion and Terrestrial Locomotion of the Northern Snakehead (Channa argus) on Multiple Substrates.

Most fishes known for terrestrial locomotion are small and/or elongate. Northern snakeheads (Channa argus) are large, air-breathing piscivores anecdotally known for terrestrial behaviors. Our goals were to determine their environmental motivations for emersion, describe their terrestrial kinematics for fish 3.0-70.0 cm and compare kinematics among four substrates. For emersion experiments, C. argus was individually placed into aquatic containers with ramps extending through the surface of the water, and exposed to 15 ecologically-relevant environmental conditions. For kinematic experiments, fish were filmed moving on moist bench liner, grass, artificial turf, and a flat or tilted rubber boat deck. Videos were digitized for analysis in MATLAB and electromyography was used to measure muscular activity. Only the low pH (4.8), high salinity (30 ppt), and high dCO2 (10% seltzer solution) treatments elicited emersion responses. While extreme, these conditions do occur in some of their native Asian swamps. Northern snakeheads >4.5 cm used a unique form of axial-appendage-based terrestrial locomotion involving cyclic oscillations of the axial body, paired with near-simultaneous movements of both pectoral fins. Individuals ≤3.5 cm used tail-flip jumps to travel on land. Northern snakeheads also moved more quickly on complex, three-dimensional substrates (e.g., grass) than on smooth substrates (e.g., bench liner), and when moving downslope. Release of snakeheads onto land by humans or accidentally by predators may be more common than voluntary emersion, but because northern snakeheads can respire air, it may be necessary to factor in the ability to spread overland into the management of this invasive species.

Emersión y locomoción terrestre de la cabeza de serpiente del norte (Channa argus) en múltiples sustratos (Emersion and terrestrial locomotion of the northern snakehead (Channa argus) on multiple substrates) La mayoría de los peces conocidos por locomoción terrestre son pequeños y/o alargados. Las cabezas de serpiente del norte (Channa argus) son grandes pesces piscívoros que respiran aire, anecdóticamente conocidos por sus comportamientos terrestres. Nuestros objetivos fueron determinar sus motivaciones ambientales para la emersión, describir su cinemática terrestre para peces de 3, 0 a 70, 0 cm y comparar la cinemática entre cuatro sustratos. Para los experimentos de emersión, C. argus se colocó individualmente en contenedores acuáticos con rampas que se extienden a través de la superficie del agua y fueron expuesto a quince condiciones ambientales ecológicamente pertinentes. Para los experimentos cinemáticos, los peces se filmaron moviéndose sobre un revestimiento de banco húmedo, césped, césped artificial y una cubierta de bote de goma plana o inclinada. Los videos se digitalizaron para su análisis en MATLAB y se usó electromiografía para medir la actividad muscular. Solo los tratamientos de bajo pH (4, 8), alta salinidad (30 partes por mil) y alto dCO2 (solución de agua de Seltz 10%) provocaron respuestas de emersión. Aunque son extremas, estas condiciones si ocurren en algunos de sus pantanos asiáticos nativos. Las cabezas de serpiente del norte >4, 5 cm usaron una forma única de locomoción terrestre basada en movimientos apéndiculares-axiales que involucra oscilaciones cíclicas del cuerpo axial, junto con movimientos casi simultáneos de ambas aletas pectorales. Los individuos de ≤3, 5 cm usaron saltos de cola para moverse en tierra. Las cabezas de serpiente del norte también se movían más rápidamente en sustratos tridimensionales complejos (ej., césped) que en sustratos lisos (ej., revestimiento de banco), y al moverse cuesta abajo. La liberación de cabezas de serpiente en la tierra por humanos o accidentalmente por depredadores puede ser más común que la emersión voluntaria, pero debido a que las cabezas de serpiente del norte pueden respirar aire, puede ser necesario tener en cuenta la capacidad de propagarse por tierra en el manejo de esta especie invasora. Translated to Spanish by YE Jimenez (yordano_jimenez@brown.edu).

Investigating anthelmintic efficacy against gastrointestinal nematodes in cattle by considering appropriate probability distributions for faecal egg count data.

The Faecal Egg Count Reduction Test (FECRT) is the most widely used field-based method for estimating anthelmintic efficacy and as an indicator of the presence of anthelmintic resistant nematodes in cattle, despite never having been validated against the gold standard of controlled slaughter studies. The objectives of this study were to assess the normality of cattle faecal egg count (FEC) data and their transformed versions, since confidence intervals used to aid the interpretation of the FECRT, are derived from data assumed to be normally distributed, and violation of this assumption could potentially lead to the misclassification of anthelmintic efficacy. Further, probability distributions and associated parameters were evaluated to determine those most appropriate for representing cattle FEC data, which could be used to estimate percentage reductions and confidence limits. FEC data were analysed from 2175 cattle on 52 farms using a McMaster method at two different diagnostic sensitivities (30 and 15 eggs per gram (epg)) and a sensitive centrifugal flotation technique (SCFT) with a sensitivity of 1 epg. FEC data obtained from all egg count methods were found to be non-normal even upon transformation; therefore, it would be recommended that confidence or credible intervals be generated using either a Bootstrapping or Bayesian approach, respectively, since analyses using these frameworks do not necessarily require the assumption of normality. FEC data obtained using the SCFT method were best represented by distributions associated with the negative binomial and hence arithmetic means could be used in FECRT calculations. Where FEC data were obtained with less sensitive counting techniques (i.e. McMaster 30 or 15 epg), zero-inflated distributions and their associated central tendency were the most appropriate and would be recommended to use, i.e. the arithmetic group mean divided by the proportion of non-zero counts present; otherwise apparent anthelmintic efficacy could be misrepresented.

Acclimation to hypoxia increases survival time of zebrafish, Danio rerio, during lethal hypoxia.

Survivorship of zebrafish, Danio rerio, was measured during lethal hypoxic stress after pretreatment in water at either ambient oxygen or at a lowered, but nonlethal, level of oxygen. Acclimation to nonlethal hypoxia (pO(2) congruent with 15 Torr; ca. 10% air-saturation) for 48 hr significantly extended survival time during more severe hypoxia (pO(2) congruent with 8 Torr; ca. 5% air-saturation) compared to survival of individuals with no prior hypoxic exposure. The magnitude of the acclimation effect depended upon the sex of the fish: hypoxia pretreatment increased the survival times of males by a factor of approximately 9 and that of females by a factor of 3 relative to controls. In addition, survival time of control and hypoxia acclimated fish depended upon when in the year experiments were conducted. Survival times were 2-3 times longer when measured in the late fall or winter compared to survival times measured during the spring or summer. These results demonstrate a direct survival benefit of short-term acclimation to hypoxia in this genetically tractable fish. The fact that the acclimation effect depended upon the sex of the fish and the season during which experiments were conducted demonstrates that other genetic and/or environmental factors affect hypoxia tolerance in this species. J. Exp. Zool. 289:266-272, 2001.

Geometric optimization of a tissue pattern for semilunar valve reconstruction.

BACKGROUND AND AIM OF THE STUDY: A novel geometric trefoil pattern has been suggested for semilunar valve reconstruction. Optimization of the geometry must rely on an appreciation of normal anatomy and knowledge of the mechanical properties of the tissue used for the reconstruction. METHODS: Computer-assisted design (CAD) was used to create an optimized leaflet geometry based on published dimensions for normal human aortic valves. The optimized leaflet geometry was subjected to finite element analysis (FEA) to study stress distribution with pressure loading of the leaflet. In vitro function of the optimized trefoil tissue pattern is being studied by static testing initially, with physiological saline. RESULTS: An optimized leaflet geometry has been developed by CAD, and further refined by FEA. Static testing of the optimized trefoil tissue pattern shows near-normal anatomy, with no prolapse or pin wheeling, and full valve competence to 90 mmHg pressure. CONCLUSIONS: An initial optimized geometry has been developed for a two-dimensional tissue pattern that can be used to reconstruct diseased semilunar heart valves with human pericardium. Optimization studies are based on the mechanical properties of the tissue, CAD to mimic normal anatomy, FEA to study stress distribution, and static load testing to confirm function.

Pre-use intraoperative testing of autologous tissue for valvular surgery: a proof of concept study.

BACKGROUND AND AIM OF THE STUDY: Autologous tissue is being used more commonly for valvular repair and reconstruction, but methods for testing the mechanical properties of the tissue intraoperatively have not been available. Before committing to its use, the surgeon should know its thickness, strength, and if it is isotropic or anisotropic. We have developed an intraoperative tissue tester (ITT), based on optical and mechanical methods that allows a surgeon to assess these parameters rapidly. METHODS: Tissue thickness was measured with a micrometer. Specimens of tissue were incrementally pressurized to 200 mmHg, resulting in a dome-shaped distortion. The dome is a section of a spheroid whose dimensions are determined by the diameter of the circle and the height of the dome. The LaPlace equation for a sphere was used to calculate tissue stress. Moire fringe patterns are visualized as concentric circles or ellipses produced by directing a beam of collimated light at 450 through a grid with Ronchi rulings onto the surface of the dome. Circles indicate isotropy and ellipses indicate anisotropy. Uniaxial testing was performed on strips of tissue taken from orthogonal and intermediate axes to validate Moire fringe pattern analysis. Specimens of human pericardium (n = 8), lightly tanned by a 10-min immersion in buffered 0.625% glutaraldehyde, were examined. RESULTS: Mean thickness of eight specimens was 0.61 mm (range: 0.41-0.99 mm). During inflation, the lightly tanned human pericardium showed non-linear deformation characteristic of pericardium. Mean peak stress for the dome was 136 kPa. There was good correlation between dome height in the inflation tester and the uniaxial Young's modulus. Moire fringe pattern analysis showed minimal anisotropy to 200 mmHg pressure, confirmed by uniaxial testing. CONCLUSIONS: The basic mechanical properties of autologous tissue to be used for valvular repair or reconstruction should be determined to avoid use of tissue that is outside an expected range of values for strength, anisotropy/isotropy and thickness. A self-contained ITT, based on optical and mechanical principles, has been developed to measure those parameters.

Autologous pericardial reconstruction of semilunar valves.

BACKGROUND AND AIMS OF THE STUDY: Previous methods for reconstructing semilunar valves have been characterized by lack of precision and reproducibility and, with one exception, the use of unsuitable biomaterial. A new method combines precision with simplicity to reconstruct aortic and pulmonary valves with lightly tanned autologous tissue supported by the annulus of the native valve. Essential components include sizing based on distance between adjacent commissures, cutting a seamless, size-specific trefoil-shaped pattern of tissue with a tricuspid orifice, temporary mounting of the pattern on disposable formers, and suturing with continuous or interrupted monofilament suture to join the autologous tissue pattern with the valve annulus. METHODS: The tissue pattern is cut and mounted on forming devices that enable the implanting surgeon to visualize the orientation clearly, and perform repair accurately and rapidly. One, two or three leaflets can be reconstructed. The forming and cutting devices are discarded when reconstruction is complete. Diseased valves can be reconstructed in no more time than is required for replacement with a prosthesis of any type. Advantages of the method include preservation of full effective orifice area, lack of need for any foreign body other than the sutures used for reconstruction, and the use of non-immunogenic autologous tissue known to be durable and resistant to calcific degeneration. Contraindications include heavily calcified annulus that cannot be satisfactorily debrided, bicuspid anatomy, or a significantly asymmetric annulus. RESULTS: Pulmonary valve reconstructions have been performed in four juvenile sheep by this method. Three animals survived five months; there was one operative death due to non-valve related causes. CONCLUSIONS: Semilunar valve reconstruction with autologous tissue can be simple, precise, and reproducible.

Clinical and cost effectiveness of the counter-rotational brush in private practice.

There have previously been no studies on the cost effectiveness of the use of a counter-rotational toothbrush (INTERPLAK Home Plaque-Removal Instrument), which has been demonstrated to be more effective than ordinary toothbrushes in reaching plaque-removal and gingival-health goals. Killoy et al studied the costs of required periodontal treatment for 32 patients with moderate periodontitis at two corporate capitation dental centers. The subjects were divided into two groups, a test group that brushed with a counter-rotational toothbrush and one that brushed with a manual toothbrush. Probing depth, attachment levels, and plaque and bleeding indexes in the test brush group were better than those in the control group. The end result was a mean reduction of $535 in the cost of periodontal treatment that had been planned before using the counter-rotational brush over 18 months, while the group using the manual brush experienced a mean increase of $11 in required treatment over original plans. Furthermore, the test group reached a state of gingival health, but the control group did not. The study concluded that the counter-rotational brush is cost effective.

Clinical assessment of the INTERPLAK toothbrush vs a conventional brush plus floss.

Thirty clinical recall patients from the University of Missouri at Kansas City School of Dentistry participated in a 4-week study to determine the long-term effectiveness of the INTERPLAK Home Plaque-Removal Instrument compared to manual brushing and flossing. Patients were divided into two groups, with each group using the INTERPLAK device for 2 months and the manual brush for 2 months. Patients were assessed according to measured indices for plaque, bleeding, crevice depth, and calculus. The study found that both kinds of brushes significantly reduced plaque, bleeding, and crevice depth; however, only the INTERPLAK brush reduced calculus. Improvements on all indices were greater for the INTERPLAK device than they were for manual brushing and flossing. At the end of the 4 months, most patients indicated that they would continue to use the INTERPLAK device.

Experimental evaluation of an autologous tissue heart valve.

The goal of the autologous tissue heart valve (ATHV) prosthesis project has been the development of a non-antigenic, non-calcifying bioprosthesis of greater durability than heterograft or homograft bioprostheses. It is made in the operating room, at a sterile work bench, during surgery for heart valve replacement. Autologous pericardium is used for valve construction after a five minute immersion in 0.6 per cent glutaraldehyde buffered to pH 7.4 with phosphate. The stent-mounted trileaflet prosthesis can be made in five minutes with a semi-automated method that uses two concentric mating stents that substitute clamping for sewing of the tissue. In vitro testing, to include pulse duplicator, accelerated wear tester, static testing for leakage and tensile strength testing, has been performed with ATHVs made with glutaraldehyde-tanned bovine and ovine pericardium. Transvalvular pressure gradients were measured at 3.3-7.3 mmHg at flow rates of 4-5 l/min. Six valves have been tested beyond 800,000,000 cycles with full opening and closing at differential closing pressures of 125 mmHg. One of the valves developed a 2mm leaflet tear after 26,000,000 cycles but the remaining five survived intact. No fractures were seen in the Dacron covered Delrin stents. Six ATHVs were implanted in juvenile sheep for five months. One animal died after five months of infective endocarditis secondary to an unrecognized deep wound infection and the other five were electively sacrificed at the same time interval. Four valves were fully competent at terminal elective cardiac catheterization and one showed minimal insufficiency attributed to a paravalvular leak. The leaflet tissue was free of generalized calcification in all instances. There was no evidence of leaflet tissue thickening or shrinkage. The mean calcium content at necropsy of the 15 leaflets from the five valves was 8.357 mg/g of tissue. There is experimental evidence that an ATHV made of pericardium treated briefly with glutaraldehyde may achieve the goal of a non-calcifying, more durable bioprosthesis.

The autogenous tissue heart valve: current status.

Residual antigenicity of xenograft tissue after glutaraldehyde tanning may be a factor that determines calcification and durability of bioprostheses. We have pursued the concept of a nonantigenic, noncalcifying, more durable bioprosthesis. We previously described a technique for rapid intraoperative fabrication of an autogenous tissue heart valve (ATHV). That technique has been modified to improve reliability and ease of learning. With the modified technique, a geometrically perfect trileaflet valve can be made in 5 minutes. Although any suitable tissue can be used, the pericardial ATHV is the subject of this report. Autogenous pericardium immersed for 5 minutes in glutaraldehyde has proven satisfactory for valve construction. In vitro testing in the pulse duplicator and accelerated life tester has shown that the stent assembly is capable of function beyond 800,000,000 cycles without failure. In vivo testing has been performed in the juvenile sheep model as described by the National Institutes of Health group. Five sheep were maintained for 5 months postimplant before sacrifice. Explanted valves showed no tissue thickening or shrinkage, problems seen with earlier valves made with untreated autogenous tissue, and the leaflets remained pliable, free of the degenerative changes usually seen in the sheep model.

The effectiveness of a counterrotational-action power toothbrush on plaque control in orthodontic patients.

This study compared counterrotational-action power toothbrushing with manual toothbrushing in effectiveness on plaque control and gingival health in 20 randomly selected orthodontic patients at the University of Missouri-Kansas City. A blind two-group crossover design was used. Gingival and plaque scores were recorded, and a prophylaxis was given to bring the plaque score to zero. Ten subjects received counterrotational power brushes, and ten subjects received manual brushes. Instructions appropriate to each brushing method were given by a hygienist. At 30 and 60 days, plaque and gingival scores were recorded and a prophylaxis was given. At 60 days the subjects who were using power brushes were switched to manual brushes, and the subjects who were using manual brushes were switched to power brushes. At 30 and 60 days, plaque and gingival scores were recorded and a prophylaxis was given. Plaque and gingival scores were significantly less (p less than 0.01) after brushing 2 months with the counterrotational power brush than with the manual brush. This finding was irrespective of the sequence in which the brushes were used.

The effectiveness of a counter-rotary action powered toothbrush and conventional toothbrush on plaque removal and gingival bleeding. A short term study.

Initial investigations have demonstrated the effectiveness of a new contra-rotary powered electric toothbrush in removing plaque supragingivally, subgingivally, and interproximally following a single use. The purpose of this study was to evaluate the effectiveness of a counter-rotary toothbrush following 1) one time instruction, 2) reinstruction and 1 week practice; and 3) a third instruction and 3 weeks of practice and home use. Twenty-four patients were studied; 12 using the counter-rotary toothbrush and 12 using a conventional toothbrush. Using O'Leary and Turesky plaque indices, both brushes significantly reduced supragingival plaque from baseline at all intervals. The counter-rotary brush, however, was more efficient than the conventional brush at all intervals (P less than 0.01). Using a Surface Area Plaque Index, both brushes significantly reduced supragingival plaque from baseline at all intervals but there were no significant differences between brushes. A timed bleeding index showed significant reduction in gingival bleeding following 28 days of brushing with both brushes. Again, the counter-rotary toothbrush was superior to the conventional toothbrush (P less than 0.01).

Effects of an air-powder abrasive system on plasma-sprayed titanium implant surfaces: an in vitro evaluation.

The purpose of this study was to conduct an in vitro evaluation of the effects of an air-powder abrasive system, commonly used in clinical dentistry for periodontal maintenance, on the surfaces of plasma-sprayed titanium dental implants. Twenty-eight plasma-coated titanium implant specimens were divided into a sterile water-treated control group and an air-powder-abrasive-treated test group. All specimens were subjected to three different in vitro testing conditions and post-treatment evaluations by scanning electron microscopy (SEM): (1) Topographical features of implant surfaces were studied before and after direct exposure to the abrasive; (2) biocompatibility of treated implant surfaces was evaluated and compared with those of control specimens via in vitro fibroblast attachment studies; and (3) the attachment of a common oral microbe to the implant surface and its subsequent removal by exposure to the air-powder abrasive were also evaluated. Results indicate that exposure of implant specimens to the air-powder abrasive for various periods resulted in only slight changes in surface topography, i.e., rounding of angles and edges of the plasma-spray coating and occasional surface pitting. Examination by SEM and a statistical comparison of the difference between the mean numbers of attached fibroblasts between control and test groups revealed no statistical significance. In both specimen groups, fibroblasts exhibited uniform attachment over the entire implant surface. A comparison of test and control groups demonstrated 100% removal of bacteria from the surfaces of test specimens exposed to the air-powder abrasive and approximately a 75% removal from control specimens exposed to sterile water.

The syndrome of calcific aortic stenosis and gastrointestinal bleeding: resolution following aortic valve replacement.

A syndrome exists in elderly patients of gastrointestinal tract bleeding (GIB) associated with calcific aortic stenosis (CAS). The bleeding, which may be chronic and massive, has been attributed to tiny mucosal vascular lesions which usually occur in the right colon. Selective mesenteric angiography is the best way to demonstrate the lesions, which are not seen on barium examination and may not been seen endoscopically. Previously, the recommended treatment has been segmental bowel resection, usually right hemicolectomy. Three patients have been seen with this syndrome of CAS-GIB. All three patients had severe CAS and chronic GIB and two of them had had previous, unsuccessful, intestinal operations for their GIB. All three patients had aortic valve replacement and the GIB stopped in all three patients after valve replacement. Possible mechanisms are discussed. It is concluded that aortic valve replacement is the treatment of choice for the syndrome of CAS-GIB.

Left ventricular pseudoaneurysm secondary to infection after coronary bypass surgery.

We present a case of left ventricular pseudoaneurysm following coronary bypass surgery. The cause was infection, dating from the bypass procedure 1 1/2 years before. Repair of pseudoaneurysm in a patient with a bypass is complicated by the presence of grafts which should be protected from injury. Details of successful management in this case are presented.