Archerfish respond to a hunting robotic conspecific.

While the unique hunting behavior of archerfish has received considerable scientific attention, the specific social cues that govern behaviors like intraspecific kleptoparasitism in the species are less understood. This paper asks whether the use of a robotic facsimile representing an archerfish can elicit a social response if it approximates an archerfish's appearance, along with key features of its hunting behavior. We found that the fish respond to the robot when it hunted, as indicated by decreasing distances between the robot and fish (and among the fish) during the robot's hunting behavior sequence, as well as higher net transfer entropy when the robot was hunting. These effects were present even when the robot's "hunt" was unproductive and did not result in food. The temporal pattern of fish approach to the robot and each other indicated that the segment of robot hunting behavior proximal to the robotic facsimile shot elicited fish behavior initially. However, earlier cues in the robot's hunting sequence became important following more experience with a food contingency. This indicates that further studies could use a robotic facsimile to conduct a detailed stimulus analysis, changing aspects of the robot's appearance and behavior to uncover the basic mechanisms of information transfer among individuals in a social hunting scenario.

Open-source five degree of freedom motion platform for investigating fish-robot interaction.

This paper presents the design, construction, operation, and validation of a robotic gantry platform specifically designed for studying fish-robot interaction. The platform has five degrees of freedom to manipulate the three-dimensional position, yaw angle, and the pitch of a lure. Additionally, it has a four-conductor slip ring that allows power and data to be transmitted to the lure for the operation of fins and other actuators that increase realism or act as stimuli to focal fish during an ethorobotic experiment. The design is open-source, low-cost, and includes purpose-built electronics, software, and hardware to make it extensible and customizable for a number of applications with varying requirements.

Development of an endoluminal intestinal attachment for a clinically applicable distraction enterogenesis device.

PURPOSE: Previous methods of distraction enterogenesis have relied upon blind-ending intestinal segments or transmural device fixation, requiring multiple operations and potential bowel injury. We hypothesized that using a novel attachment would allow reversible device coupling to the luminal bowel surface, achieving effective endoluminal distraction. METHODS: A telescopic hydraulic device was designed with latex balloon attachments covered with high-friction mesh and a dilating fenestrated elastic mask (DFM attachment), allowing mesh-to-mucosa contact only with inflation. Yorkshire pigs underwent jejunal Roux-en-Y limb creation and device placement via jejunostomy. Devices underwent 3 cycles of balloon inflation and hydraulic extension/retraction per day for 7 days and then explanted and studied for efficacy. RESULTS: DFM attachment allowed reversible, high-strength endoluminal coupling without tissue injury or reduction in bowel perfusion. After 7 day implant, distracted bowel achieved a 44 ± 2% increase in length vs. fed, nondistracted bowel, corresponding to a gain of 7.1 ± 0.3 cm. Distracted bowel demonstrated increased epithelial cell proliferation vs. control bowel. Attachment sites demonstrated villus flattening, increased crypt depth, thicker muscularis mucosa, and unchanged muscularis propria thickness vs. CONCLUSION: Novel high-strength, reversible attachments enabled fully endoluminal distraction enterogenesis, achieving length gains comparable to open surgical techniques. This approach may allow development of clinically applicable technology for SBS treatment.

Development of a novel approach to safely couple the intestine to a distraction-induced device for intestinal growth: use of reconstructive tissue matrix.

BACKGROUND: Distraction-induced intestinal growth may be a novel treatment for short bowel syndrome. Longitudinal, distractive tension created by the application of force creates a significant challenge: to produce adequate force, yet not cause perforation at the fixation points. This paper describes our development of a coupling strategy to allow for successful bowel lengthening. METHODS: A curvilinear hydraulic device was implanted in an isolated Roux limb of small bowel in young Yorkshire pigs. Bowel was lengthened over a 2-week period. Study groups included: Group 1: Twelve silk transmural anchoring sutures into an engineered-coupling ring at the ends of each device. Group 2: Addition of felt pledgets to the coupling rings on the serosal surface of the small bowel. Group 3: Extraluminal use of either thin AlloDerm(®), thick AlloDerm(®), or Strattice™ mesh to anchor the device. RESULTS: Group 1 (suture-only) resulted in a gradual pulling through the suture with increasing tension and no lengthening. Felt pledgets eroded in a similar fashion, causing abdominal sepsis. Thin AlloDerm(®) failed to prevent erosion; however, it protected against gross contamination. Animals in which either thick AlloDerm(®) or Strattice™ mesh was used survived complication free to the study endpoint. Both thick AlloDerm(®) and Strattice™ prevented erosion and perforation allowing for an average of 10.85 cm expansion. CONCLUSION: This study demonstrates the use of either thick AlloDerm(®) or Strattice™ reconstructive tissue matrix which allows for safe and effective coupling. Further, we suggest this approach could be an adjunct to esophageal lengthening procedures.

Mesenteric neovascularization with distraction-induced intestinal growth: enterogenesis.

BACKGROUND: Distraction-induced enterogenesis, whereby the intestine lengthens with application of linear forces, is an emerging area which may provide a unique treatment for short bowel syndrome. With an increase in overall tissue mass, there is an increase in oxygen and nutrient demand. We hypothesized that a neovascularization within the mesentery is necessary to support the growing small bowel. METHODS: A curvilinear hydraulic device was used to induce growth within the small bowel of Yorkshire pigs, and the intestine was harvested after 14 days. High-resolution gross pictures were recorded of the mesentery at implantation and at harvest, and CT imaging of the bowel and mesentery was performed at harvest after dye injection. RESULTS: After 2 weeks of distraction, an average of 72.5 % (8.7 cm) bowel lengthening was achieved. Gross images of the mesentery between major vessels showed a blossoming of the microvasculature and this was confirmed by CT imaging with 3D reconstruction. Mesenteric sample taken from the distracted segment had a fourfold increase in the volume of microvasculature versus controls. CONCLUSION: Enterogenesis results not only in increased bowel length, but also significant increase in the mesenteric microvascularity. Presumably, this sustains the lengthened segment after application of longitudinal forces.

Flow through a mechanical distraction enterogenesis device: a pilot test.

BACKGROUND: We tested the coupling portion of a prototype intraluminal distraction enterogenesis device to allow flow-through of simulated enteric contents (SEC) in both pig and human jejunum. MATERIALS AND METHODS: SEC was made using 80% corn syrup. Ten-cm pig and human intestinal segments had a spoke-shaped 2.2 cm coupling adaptor sutured in place, intraluminally. The adaptor had a flow-through area of 33.6 mm(2). SEC was pumped into the proximal part of the intestinal segment at 0.083 mL/s. The times to first passage of SEC through the coupler (first drop), 10 mL, and 20 mL of SEC eluted from the distal end were recorded. RESULTS: Mean time to first drop elution was 155 ± 38 s with pig, and 149 ± 22 s with human bowel (P = 0.8). This corresponded to a hydrostatic pressure of 37.5 mmHg before the initial drop passed through. Mean flow rates were 0.094 mL/s in pig bowel and 0.084 mL/s in human bowel (P = 0.09). To account for occlusion from luminal debris, a 75% occlusion of coupler holes was studied in the smaller pig bowel to investigate if reductions in flow-through area could be tolerated. Mean time to first drop increased slightly to 171 ± 15 s, but the elution rate stayed the same (P = 0.5). CONCLUSIONS: After a physiologic level of initial pressure buildup allowing the first drop of SEC to pass the coupling adaptor, our prototype intestinal coupling adaptor did not obstruct flow-through of SEC, even after a 75% decrease in flow-through area. This type of attachment represents a viable approach to placing a device in-continuity without obstructing flow of enteric contents.

Application of distractive forces to the small intestine: defining safe limits.

BACKGROUND: Distraction enterogenesis is a novel method for increasing small bowel length by the application of linearly directed forces. However, the magnitude of distractive forces that human and animal small bowel can safely withstand is unknown. METHODS: Acute ex vivo force-displacement curves for human (n = 5) and pig (n = 6) small intestine (with and without mesentery) were made by applying increasing amounts of distractive forces to bowel immersed in normal saline (39°C). Progressive load was applied until gross disruption of the tissue was detected, or the applied force reached 1000 gram-force (gf). Histology was used to detect evidence of load-induced damage. In vivo blood flow to pig bowel with distractive loads (30-200 gf) was measured by laser Doppler. RESULTS: The relationship between the level of force and degree of displacement was linear. The presence of a mesentery increased stiffness of pig bowel, but did not affect human bowel. Gross tissue disruption in pig and human tissue was seen at forces between 235 and 295 gf, respectively. However, in grossly undamaged areas, histology was unchanged even after application of higher loads. With in vivo testing, mesenteric blood flow was present up to 200 gf; however, blood flow to the bowel wall was reduced to undetectable levels at loads exceeding 100 gf. CONCLUSIONS: While whole bowel tissue may tolerate greater applied loads, blood flow to the bowel wall was compromised at loads over 100 gf, suggesting that any higher forces place the bowel at risk for ischemia. These measurements will help guide the clinical application of distraction enterogenesis.

Numerical simulation of saccular aneurysm hemodynamics: influence of morphology on rupture risk.

The governing equations for pulsatile fluid flow were solved in their finite volume formulation in order to simulate blood flow in a variety of three-dimensional aneurysm geometries. The influence of geometric factors on flow patterns and fluid mechanical forces was studied with the goal of identifying the risk of aneurysm rupture. Aneurysm morphology was characterized by quantitative shape indices reflecting the three dimensionality of the vasculature derived from clinical studies. Recirculation zones and secondary flows were observed in aneurysms and arteries. Regions of extreme and alternating shear stress were observed and identified as sites for potential aneurysm rupture. The ellipticity of an aneurysm was observed to be strongly correlated with wall shear stress at the aneurysm fundus, while its non-sphericity, volume, and degree of undulation were more weakly correlated.