Cyclodextrin Polymer Preserves Sirolimus Activity and Local Persistence for Antifibrotic Delivery over the Time Course of Wound Healing.

Fibrosis and dysphagic stricture of the esophagus is a major unaddressed problem often accompanying endoscopic removal of esophageal cancers and precancerous lesions. While weekly injections of antiproliferative agents show potential for improved healing, repeated injections are unlikely clinically and may alternatively be replaced by creating an esophageal drug delivery system. Affinity-based polymers have previously shown success for continuous delivery of small molecules for weeks to months. Herein, we explored the potential of an affinity-based microparticle to provide long-term release of an antiproliferative drug, sirolimus. In molecular docking simulations and surface plasmon resonance experiments, sirolimus was found to have suitable affinity for beta-cyclodextrin, while dextran, as a low affinity control, was validated. Polymerized beta-cyclodextrin microparticles exhibited 30 consecutive days of delivery of sirolimus during in vitro release studies. In total, the polymerized beta-cyclodextrin microparticles released 36.9 mg of sirolimus per milligram of polymer after one month of incubation in vitro. Taking daily drug release aliquots and applying them to PT-K75 porcine mucosal fibroblasts, we observed that cyclodextrin microparticle delivery preserved bioactivity of sirolimus inhibiting proliferation by 27-67% and migration of fibroblasts by 28-100% of buffer treated controls in vitro. Testing for esophageal injection site losses, no significant loss was incurred under simulated saliva flow for 10 min, and 16.7% of fluorescently labeled polymerized cyclodextrin microparticle signal was retained at 28 days after submucosal injection in esophageal tissue ex vivo versus only 4% of the initial amount remaining for free dye molecules injected alone. By combining affinity-based drug delivery for continuous long-term release with a microparticle platform that is injectable yet remains localized in tissue interstitium, this combination platform demonstrates promise for preventing esophageal fibrosis and stricture.

Creation of an animal model for long gap pure esophageal atresia.

INTRODUCTION: Long gap pure esophageal atresia (LGPEA) is a congenital disorder in which the esophagus is in discontinuity, and the proximal and distal ends cannot be anastomosed in a primary fashion. No animal model for pure esophageal atresia exists. Here we describe a survival animal model for LGPEA, which will ultimately serve to test novel devices and techniques to restore continuity. METHODS: A non-survival study was first conducted in six rabbits to refine a protocol for the survival model. An open gastrostomy tube was placed, followed by a partial esophagectomy. Next, a survival study was performed with seven rabbits in which the same procedures were performed. Finally, the procedure was optimized in domestic swine. RESULTS: Despite developing the techniques and gaining valuable information in the non-survival study, none of the rabbits in the survival portion of the study lived beyond post-operative day four. Due to this complication with the rabbit, the LGPEA model was attempted in a porcine model. The pig survived to post-operative day ten, and was healthy enough to be used for further study. CONCLUSION: A porcine model of long gap pure esophageal atresia was developed which is effective and feasible to be used for testing new methods of treatment of LGPEA.

Porcine Abdominal Wall Simulator for Laparotomy Incision and Closure.

We describe an economical and simple abdominal wall model that provides a realistic experience for trainees as they develop the skills of creating an abdominal incision through the midline, followed by closure of the fascia and skin.

Commercially available biological mesh does not prevent stricture after esophageal mucosectomy.

BACKGROUND AND STUDY AIMS: Endoscopic mucosal resection (EMR) offers a minimally invasive therapy for advanced esophageal dysplasia and early cancers but stricture formation limits its applicability. We aimed at assessing the efficacy of placement of a commercially available biological mesh for preventing stricture formation following esophageal EMR. METHODS: 25 swine were submitted to circumferential esophageal EMR with 10-cm extent and divided in five groups: one group with EMR only (control); one receiving an uncovered stent (stent-only group); and three groups receiving a stent covered with one of three extracellular matrices, namely small intestine submucosa (SIS group), acellular dermal matrix (ADM group), or urinary bladder matrix (UBM group). Stricture formation was evaluated with weekly esophagograms. RESULTS: The stent-only group had significantly less stricture formation and survival was extended compared with controls (4.8 vs. 2.4 weeks). Compared with stenting only, the addition of a biological mesh did not reduce stricture formation: percent reductions in esophageal diameter for the groups were SIS 86 %, ADM 94 %, and UBM 94 %, compared with 82 % in the stent-only group. CONCLUSIONS: Placement of commercially available biological meshes did not alter remodeling sufficiently to prevent stricture formation after esophageal EMR.

Preliminary results of antiscarring therapy in the prevention of postendoscopic esophageal mucosectomy strictures.

BACKGROUND: Esophageal endoscopic submucosal dissection (ESD) is an effective minimally invasive therapy for early esophageal cancer and high-grade Barrett dysplasia. However, esophageal stricture formation after circumferential or large ESD has limited its wide adoption. Mitomycin C (MMC), halofuginone (Hal), and transforming growth factor ß3 (TGF-ß3) exhibits antiscarring effects that may prevent post-ESD stricture formation. METHODS: Using endoscopic mucosectomy (EEM) technique, an 8- to 10-cm-long circumferential esophageal mucosal segment was excised in a porcine model. The site was either untreated (control, n = 6) or received 40 evenly distributed injections of antiscarring agent immediately and at weeks 1 and 2. High and low doses were used: MMC 5 mg (n = 2), 0.5 mg (n = 2); Hal 5 mg (n = 2), 1.5 mg (n = 2), 0.5 mg (n = 2); TGF-ß3 2 µg (n = 2), 0.5 µg (n = 2). The degree of stricture formation was determined by the percentage reduction of the esophageal lumen on weekly fluoroscopic examination. Animals were euthanized when strictures exceeded 80 % or the animals were unable to maintain weight. RESULTS: The control group had a luminal diameter reduction of 78.2 ± 10.9 % by 2 weeks and were euthanized by week 3. Compared at 2 weeks, the Hal group showed a decrease in mean stricture formation (68.4 % low dose, 57.7 % high dose), while both TGF-ß3 dosage groups showed no significant change (65.3 % low dose, 76.2 % high dose). MMC was most effective in stricture prevention (53.6 % low dose, 35 % high dose). Of concern, the esophageal wall treated with high-dose MMC appeared to be necrotic and eventually led to perforation. In contrast, low dose MMC, TGF-ß3 and Hal treated areas appeared re-epithelialized and healthy. CONCLUSIONS: Preliminary data on MMC and Hal demonstrated promise in reducing esophageal stricture formation after EEM. More animal data are needed to perform adequate statistical analysis in order to determine overall efficacy of antiscarring therapy.

A novel over-the-scope deployment method for enteral stent placement.

BACKGROUND: Over the last two decades, self-expanding enteral stents have gained popularity and shown therapeutic potential for strictures, obstructions, fistulae, and perforations of the gastrointestinal (GI) tract. Currently available stent delivery systems make deployment in many locations in the GI tract difficult due to the inability to traverse curves or impossible due to the size requirements of the deployment systems. METHODS: A 67-year-old male presented to our hospital with severe gallstone pancreatitis, requiring a prolonged intensive care unit course. Two days after discharge to a rehabilitation facility he developed acute abdominal pain and pneumoperitoneum. Operative exploration failed to identify a perforation. Subsequently, a left-upper-quadrant abscess developed that was drained percutaneously, yielding coliform bacteria. The drain produced several hundred milliliters of stool a day. A barium enema demonstrated a perforation in the descending colon from an old colo-colic anastomosis site. We proposed a novel over-the-scope (OTS) stent deployment method. Utilizing a heat-activated polymer sheath, the stent was affixed to the endoscope. A modified speed-banding attachment was created to permit release of the polymer sheath once endoscopic and fluoroscopic confirmation of the correct position was obtained. RESULTS: Utilizing this method of OTS stent deployment, a fully covered 23 × 155 mm self-expanding metal stent (WallFlex, Boston Scientific, Natick, MA) was placed in the colon. Endoscopic and fluoroscopic evaluation following stent placement confirmed stent coverage of the perforation with no ongoing evidence of leak. The patient was discharged to his home state 2 weeks after stent placement in stable condition. CONCLUSION: We have developed a novel method of OTS stent placement that permits deployment of a variety of enteral stents on any available endoscope. This method permits placement of fully covered stents in locations in the GI tract not reachable with currently available delivery systems.

Biodegradable esophageal stent placement does not prevent high-grade stricture formation after circumferential mucosal resection in a porcine model.

BACKGROUND: Advanced esophageal dysplasia and early cancers have been treated traditionally with esophagectomy. Endoscopic esophageal mucosectomy (EEM) offers less-invasive therapy, but high-degree stricture formation limits its applicability. We hypothesized that placement of a biodegradable stent (BD-stent) immediately after circumferential EEM would prevent stricturing. METHODS: Ten pigs (five unstented controls, five BD-stent) were utilized. Under anesthesia, a flexible endoscope with a band ligator and snare was used to incise the mucosa approximately 20 cm proximal to the lower esophageal sphincter. A 10-cm, circumferential, mucosal segment was dissected and excised by using snare electrocautery. In the stented group, an 18-×120-mm, self-expanding, woven polydioxanone stent (ELLA-CS, Hradec-Kralove) was deployed. Weekly esophagograms evaluated for percent reduction in esophageal diameter, stricture length, and proximal esophageal dilation. Animals were euthanized when the stricture exceeded 80% and were unable to gain weight (despite high-calorie liquid diet) or at 14 weeks. RESULTS: The control group rapidly developed esophageal strictures; no animal survived beyond the third week of evaluation. At 2 weeks post-EEM, the BD-stent group had a significant reduction in esophageal diameter (77.7 vs. 26.6%, p < 0.001) and degree of proximal dilation (175 vs. 131%, p = 0.04) compared with controls. Survival in the BD-stent group was significantly longer than in the control group (9.2 vs. 2.4 weeks, p = 0.01). However, all BD-stent animals ultimately developed clinically significant strictures (range, 4-14 weeks). Comparison between the maximum reduction in esophageal diameter and stricture length (immediately before euthanasia) demonstrated no differences between the groups. CONCLUSIONS: Circumferential EEM results in severe stricture formation and clinical deterioration within 3 weeks. BD-stent placement significantly delays the time of clinical deterioration from 2.4 to 9.2 weeks, but does not affect the maximum reduction in esophageal diameter or proximal esophageal dilatation. The timing of stricture formation in the BD-stent group correlated with the loss radial force and stent disintegration.

Comparison of anterior transgastric access techniques for natural orifice translumenal endoscopic surgery.

BACKGROUND: The advancement of natural orifice translumenal endoscopic surgery (NOTES) into clinical practice is dependent on its safety, efficacy, and efficiency. Access is the obligatory first step in NOTES and serves as a surrogate to technical difficulties associated with this novel surgical approach. This study aimed to compare endoscopic transgastric access techniques in terms of safety, reproducibility, and efficiency. METHODS: Seven variations for anterior transgastric NOTES access were evaluated with female domestic swine. After marking of an anterior site, electrocautery was used to create a small gastrotomy, followed by balloon dilation and entry into the peritoneal cavity. Methodologic variations incorporated the use of guidewires, electrocautery and dilation combined within a single device, support tubes, and dilation without electrocautery. Access times were recorded, and tissue injury was evaluated. RESULTS: In 70 access attempts, the most serious complication was bleeding from the gastroepiploic vessel, controlled with electrocautery. High variability in access times was prevalent with almost all the access techniques. CONCLUSIONS: This study supports the presumption that an anterior transgastric access technique for NOTES procedures is safe. The use of a wire to mark the site and another wire to retain the gastrotomy provided safe, efficient, and reproducible transgastric access. Comparison with laparoscopy exposed the disparity in technical challenges facing NOTES, suggesting that new technology and further refinement in methodology are required for NOTES to be clinically relevant.

Endoscopic access to and exploration of the lesser sac in a human cadaver model: opportunity for transgastric endoscopic pancreatic surgery (with video).

BACKGROUND: Transgastric endoscopy may represent a viable platform for diagnostic and therapeutic pancreatic interventions with reduced morbidity. In a human cadaver model, we aimed to determine the feasibility of transgastric endoscopic access to the lesser sac, creation of an adequate working space within the lesser sac, and reliable identification of lesser sac anatomic structures. METHODS: In six human cadavers, endoscopic guidance was used to determine an appropriate access site to the lesser sac. Subsequently, endosonographic guidance was used to introduce an aspiration needle into the potential space between the stomach and the pancreas. After creating a fluid cushion and dilating the needle tract, an endoscope was advanced through the gastrotomy into the lesser sac and air insufflation was used to create a working space. Predetermined anatomic structures were systematically sought and marked when recognized. In the final two cadavers, endoscopic closure of the access site was performed. RESULTS: All six procedures were successful in achieving access to the lesser sac and establishing an adequate working space. The access sites appeared amenable to endoscopic closure. Reliable organ identification, however, was not achieved in all cases, representing one of the immediate barriers to clinical application. CONCLUSIONS: Transgastric endoscopic access to the lesser sac can be achieved reliably and an adequate working space can be established. Additional research addressing endoscopic orientation and organ recognition within the lesser sac is necessary. The immediate potential applications of this approach include differentiating benign from malignant pancreatic pathology.

Initial evaluation of a novel, prototype, forward-viewing echoendoscope in a porcine arterial bleeding model (with video).

BACKGROUND: Real-time visualization of submucosal arterial flow at the base of an ulcer might improve endoscopic hemostasis by permitting more accurate assessment of the artery, precise targeting of therapy, and confirmation of vessel ablation. OBJECTIVE: To evaluate the utility of a novel, forward-viewing echoendoscope in identifying bleeding submucosal arteries, guiding hemostatic therapy, and confirming cessation of flow through treated vessels. DESIGN: In 7 pigs, a previously described porcine model for peptic ulcer hemorrhage was created by isolating the gastroepiploic and/or short gastric artery and tunneling it into the subserosal space at laparotomy. SETTING: Animal research facility. INTERVENTION: The prototype endoscope was used to image submucosal arterial flow. EUS guidance was then used to deliver endoscopic hemostatic therapy and assess treatment adequacy. MAIN OUTCOME MEASUREMENTS: Identification of the target submucosal artery and successful delivery of EUS-guided endoscopic therapy, evidenced by cessation of Doppler flow through the target vessel. RESULTS: Tunneled arteries were visualized endosonographically in all 7 cases. EUS-guided submucosal injection of epinephrine was successful in 2 of 2 cases. EUS-guided delivery of thermal hemostatic therapy was successful in 2 of 4 cases. Absence of flow through treated vessels was confirmed in cases in which EUS-guided therapy was successfully delivered. LIMITATIONS: Acute animal model. CONCLUSION: Proof of principle experiments in a porcine peptic ulcer hemorrhage model suggest that real-time sonographic imaging of submucosal arteries is feasible with a forward-viewing echoendoscope, and guided hemostatic therapy can be delivered.

The diagnostic efficacy of natural orifice transluminal endoscopic surgery: is there a role in the intensive care unit?

BACKGROUND: Evaluation of a potential source for abdominal sepsis in a critically ill patient can be challenging. With flexible endoscopy readily available in this setting, we sought to evaluate the diagnostic efficacy of a transgastric natural orifice transluminal endoscopic surgery (NOTES) peritoneoscopy vs. laparoscopic exploration in the identification of intra-abdominal pathology in a porcine model. METHODS: In this acute study, 15 pigs were randomized to demonstrate 0 to 4 pathologic lesions: small bowel ischemia (SBI), small bowel perforation (SBP), colon perforation (CP), and gangrenous cholecystitis (GC). Two blinded surgical endoscopists were allowed 60 min to perform NOTES or laparoscopy (LAP) to correctly identify or exclude each lesion. A prototype endoscope (R-scope, Olympus, Inc), which enables independent instrument mobility, was used in the NOTES arm. RESULTS: When considering all lesions, LAP was more sensitive diagnostically than NOTES (77.4% vs. 61.3%) overall. LAP also displayed a slightly higher NPV compared with NOTES (79.4% vs. 70.7%). However, NOTES was 100% specific with 100% positive predictive value (PPV) compared with 93.1% and 92.3% with LAP, respectively. Individually, NOTES was found most sensitive with CP identification (87.5%) and least sensitive with SBP (37.5%). The sensitivity of NOTES for SBI and GC was 62.5% and 57.1%, respectively. CONCLUSIONS: The utilization of NOTES as a diagnostic tool may have an important role in the critically ill patient when operative intervention is highly morbid. Although it may be overall inferior diagnostically compared with laparoscopy, a positive identification was highly specific with a strong predictive value. Further investigation addressing an improved small bowel evaluation technique would be beneficial. A human trial of NOTES in the ICU utilizing the current technology would still initially mandate laparoscopic or open surgical confirmation and treatment.

Hydroperitoneum-facilitated EUS-guided peritoneal entry and closure of alternate access sites for NOTES.

BACKGROUND: Access sites other than the anterior gastric wall may provide improved ergonomics for natural orifice transluminal endoscopic surgery (NOTES). Endoscopic ultrasound (EUS) guidance significantly reduces, but does not eliminate, risk of access through these alternate sites. This study evaluates the utility of hydroperitoneum as an adjunct to EUS-guided access and closure of alternate access sites for NOTES. METHODS: Access and closure procedures were initially performed with EUS guidance alone, and subsequently, because of complications resulting from this technique, the procedures were performed with the aid of a transabdominal hydroperitoneum. RESULTS: In this nonrandomized study, 6 access and closure procedures performed with EUS guidance alone resulted in 4 complications. After modifying the technique to incorporate pre-access hydroperitoneum, 7 EUS-guided access and closure procedures were performed without significant complications. CONCLUSIONS: Hydroperitoneum appears to be an effective adjunct to ensure the safety of EUS-guided peritoneal entry and closure of alternate access sites for NOTES.

EUS in localizing safe alternate access sites for natural orifice transluminal endoscopic surgery: initial experience in a porcine model.

BACKGROUND: Most natural orifice transluminal endoscopic surgery (NOTES) procedures have been performed through the anterior stomach wall, based on the established safety of PEG placement. This approach does not afford mechanically efficient access to all anatomic areas of interest. OBJECTIVE: To assess the utility of EUS in identifying safe alternate access sites for NOTES. DESIGN: Nonsurvival animal experiment. METHODS: Thirty-two EUS-guided access procedures were performed through the antrum, the posterior stomach wall, or the rectum of 12 pigs. Sixteen safe-access procedures (SAP) used sonographic guidance to achieve safe intraperitoneal access by avoiding extraluminal organs and vessels during the initial NOTES puncture. Sixteen unsafe-access procedures (UAP) evaluated potential complications of blind access by performing a standard NOTES puncture at sites adjacent to critical extraluminal structures identified by EUS. Access was achieved by using a similar technique for both SAPs and UAPs. Baseline and completion laparotomies were performed. RESULTS: All 16 UAPs resulted in clinically relevant complications, such as liver laceration and iliac artery injury. In contrast, 13 SAPs were without complication. The 3 complications in the SAP group occurred with transrectal access and consisted of 2 minor complications and a small-bowel perforation. CONCLUSIONS: Blind NOTES access through the antrum, posterior stomach wall, and rectum could result in catastrophic complications. In contrast, EUS-guided access through these sites substantially reduced but did not completely eliminate this risk. EUS appears promising as an adjunct to NOTES access, particularly as more experience is gained in definitively excluding the presence of at-risk extraluminal structures.

Magnetic compression anastomosis (magnamosis) in a porcine esophagus: Proof of concept for potential application in esophageal atresia.

BACKGROUND: Magnetic compression anastomosis (magnamosis) is the process of forming a sutureless anastomosis of the gastrointestinal tract using two magnetic Harrison rings. It has been shown to be effective in stomach, small bowel and colon, but has not been implemented in the esophagus. A pure esophageal atresia porcine model was developed to test the concept. METHODS: Five pigs weighing between 35 and 65 kg were used. In all pigs, a percutaneous endoscopic gastrostomy (PEG) tube was placed, and a right thoracotomy was performed. Esophageal atresia was simulated by transecting the esophagus with a cutting stapler, and magnets were placed endoscopically to approximate the two ends of the esophagus. In the first pig, the tissue within the magnetic ring was excised endoscopically to achieve immediate patency. In the second pig, approximation of the blind esophageal ends was reinforced with 3-4 externally-placed sutures but immediate patency was not performed. In the last three pigs, both external suture reinforcement and immediate patency were performed. The pigs survived for 10-14 days and received nutrition through PEG tube. At necropsy, an esophagram was performed, the specimen was explanted and a leak test was performed. RESULTS: The first pig died in the early postoperative period from a leak owing to separation of the magnets. The second pig died from aspiration before the anastomosis formed. The last three pigs survived until the study endpoint. The third pig had a contained leak owing to the staple line being placed between the magnets; this was not clinically significant. The last two pigs had well-formed anastomoses. Burst tests showed no leak when injecting saline up to 30 mmHg. CONCLUSION: Magnamosis is technically feasible for esophagoesophageal anastomoses. A survival model for pure esophageal atresia was developed and refined in pigs. Further work in this area may lead to clinical use in humans.

Infectious implications in the porcine model of natural orifice transluminal endoscopic surgery (NOTES) with PEG-tube closure: a quantitative bacteriologic study.

BACKGROUND: Obtaining reliable closure of transvisceral defects currently limits natural orifice transluminal endoscopic surgery (NOTES). PEG tubes are potential means of managing NOTES gastrotomies. OBJECTIVE: To determine the efficacy of PEG closure after NOTES. DESIGN: An experimental animal study. SETTING: A laboratory. INTERVENTIONS: The pigs received gastric lavage with saline solution, chloramphenicol, or no lavage, and then underwent transgastric NOTES peritoneoscopy. Cultures were obtained by endoscopy during the surgery. A sterile foreign body was left in the peritoneal cavity. The gastrotomy was closed with a 20F PEG tube. The animals were observed for 14 days and underwent sterile laparotomy. Cultures of the foreign body and the peritoneal cavity were obtained. MAIN OUTCOME MEASUREMENTS: Abscess rate, peritoneal quantitative cultures. RESULTS: After 1 exclusion for anesthetic complications, 19 animals underwent NOTES; 18 (94.7%) survived the entire postoperative period. One animal died on postoperative day 2 after the PEG tube dislodged. At 14 days, 5 animals (27.8%) had intra-abdominal abscesses, 8 (44.4%) had positive peritoneal cultures, and 9 (50%) foreign bodies were contaminated on culture. Infectious complications were not altered by the type of gastric lavage or peritoneal bacterial inoculum introduced at the time of surgery. LIMITATION: An animal model. CONCLUSIONS: PEG closure of a NOTES gastrotomy is associated with subclinical intra-abdominal abscess formation and can result in death when the tube is dislodged during the early postoperative period. Preprocedural gastric lavage does not alter the intra-abdominal bacterial burden introduced at the time of surgery or subsequent infectious outcomes in the porcine model. These concerning findings necessitate additional studies to determine if porcine models are appropriate and applicable to human subjects in the NOTES setting.

Complete endoscopic closure of gastric defects using a full-thickness tissue plicating device.

Obtaining endolumenal closure of hollow visceral defects may complement conventional, incision-based, surgical alternatives and benefit the experimental field of natural orifice translumenal endoscopic surgery (NOTES). Endoscopic tissue plicating devices (TPD) represent a promising closure technology; however, the long-term integrity of resultant closures is uncertain. Swine (n=10) underwent survival transgastric NOTES peritoneoscopy procedures with TPD gastrotomy closure while device performance and closure integrity were evaluated. Following uncomplicated procedures, no animals revealed leakage on upper gastrointestinal contrast fluoroscopy immediately following closure and on postoperative days 2 and 7. Necropsy performed on the 14th postoperative day revealed a subclinical colonic injury for one animal; the remaining nine animals had no complications. Gastric burst testing revealed the strength of closure was comparable to that of nonsurgical control stomachs (85.1 vs. 85.3 mm Hg, p=0.98). For six of nine (66%) TPD animals, bursting occurred remote to the closure site in nonsurgical tissue, indicating that closure strength equaled that of native tissue. Endoscopic TPD closure of standardized NOTES gastric defects results in strong, leak-proof closure; however, injuries can occur. These findings support evaluation of TPD closure in human trials involving noncontrolled gastric defects.

Quantitative evaluation of 2-deoxy-2[F-18]fluoro-D-glucose-positron emission tomography imaging on the woodchuck model of hepatocellular carcinoma with histological correlation.

PURPOSE: The Eastern woodchuck (Marmota monax) is considered as a naturally occurring animal model of hepatocellular carcinoma (HCC). The performance of 2-deoxy-2-[F-18]fluoro-D-glucose (FDG) for imaging HCC on the woodchuck using Positron emission tomography (PET) was investigated in this study. PROCEDURES: Dynamic FDG-PET scans were performed on five woodchucks with HCC and one healthy woodchuck before removal and processing of the liver tissues for histology. The parameters of a two-tissue compartment model with dual input were estimated using weighted least squares (WLS). RESULTS: Ten HCCs were confirmed histologically. Six HCCs had a tumor-to-liver standardized uptake value (SUV) ratio < or =1.15, a k (4) / k (3) ratio similar to that in hepatic tissues and were well-differentiated. Four HCCs had a tumor-to-liver SUV ratio >1.15, a lower k (4) / k (3) ratio than the hepatic tissues and were moderately differentiated. CONCLUSIONS: Increased FDG uptake was observed in HCCs that were the least differentiated and correlated with a lower k (4) / k (3) ratio.

A colorimetric assay method to measure acetyl-CoA synthetase activity: application to woodchuck model of hepatitis virus-induced hepatocellular carcinoma.

A new spectrophotometric method for quantitation of acetyl-CoA synthetase (ACAS) activity is developed. It has been applied for ACAS assay in the liver tissues of a woodchuck model of hepatitis virus-induced hepatocellular carcinoma (HCC). The assay is based on the established pyrophosphate (PPi) detection system. ACAS activity is indexed by the amount of PPi, the product of ACAS reaction system of activated form of acetate (acetyl-CoA) with ACAS catalysis. PPi is determined quantitatively as the amount of chromophore formed with molybdate reagent, 1-amino-2-naphthol-4-sulfonic acid in bisulfite and 2-mercaptoethanol. PPi reacts with molybdate reagent to produce phosphomolybdate and PPi-molybdate complexes. 2-mercaptoethanol is responsible for color formation which has the peak absorbance at 580 nm. This method was sensitive from 1 to 20 nmol of PPi in a 380-mul sample (1-cm cuvette). A ten-fold excess of Pi did not interfere with the determination of PPi. To study the major metabolic pathways of imaging tracer [1-(11)C]-acetate in tumors for detection of HCC by Positron Emission Tomography (PET), the activity of one of the key enzymes involved in acetate or [1-(11)C]-acetate metabolism, ACAS was assayed by this newly developed assay in the tissue samples of woodchuck HCCs. A significant increase of ACAS activity was observed in the liver tissues of woodchuck HCCs as compared with neighboring regions surrounding the tumors (P<0.05). The respective ACAS activities in the subcellular locations were also significantly higher in HCCs than in the surrounding tissues (P<0.05) (total soluble fraction: 876.61+/-34.64 vs. 361.62+/-49.97 mU/g tissue; cytoplasmic fraction: 1122.02+/-112.39 vs. 732.32+/-84.44 mU/g tissue; organelle content: 815.79+/-100.77 vs. 547.91+/-97.05 mU/ g tissue; sedimentable fragment: 251.92+/-51.56 vs. 90.94+/-18.98 mU/ g tissue). The finding suggests an increase in ACAS activity in the liver cancer of woodchuck models of HCC as compared to that in the normal woodchuck liver. The developed assay is rapid, simple and accurate and is suitable for the investigation of ACAS activity under physiologic and pathophysiologic conditions.

Creation of an Esophageal Atresia Animal Model Using a Bifurcated Esophagus to Maintain Digestive Tract Continuity.

INTRODUCTION: We previously developed a porcine model of long gap pure esophageal atresia (EA) to aid in the creation of novel devices and techniques for treatment of EA. Shortcomings of the model included difficulty decompressing the proximal esophageal pouch (leading to recurrent aspiration) and a requirement for gastrostomy tube (G-tube) feeds. Therefore, we sought to create a porcine model with a bifurcated esophagus wherein one portion of the esophageal lumen retained patency and the other part mimicked EA. METHODS: After G-tube placement, thoracotomy was performed with subsequent partial stapled transection of the esophagus in a transverse manner, followed by longitudinal, partial stapled transection of the esophagus proximally and distally. Magnets were placed in the esophageal pouches. RESULTS: Proximal and distal esophageal pouches were created while preserving a parallel, narrower segment of continuous esophagus. G-tube feeds were used initially, but the animal ultimately tolerated full nutrition by mouth. The magnets successfully restored esophageal continuity. The animal regained much of the initial weight lost and survived to planned euthanasia. Necropsy revealed anastomosis formation without evidence of leak. CONCLUSIONS: A bifurcated porcine esophagus model was successfully devised, simulating EA while allowing the animal to receive oral feeds and clear oral secretions. This model is anticipated to promote animal well-being and ease of care during future investigations, as well as a platform for the safe development of new therapies for EA.

Assessing the Adequacy of Absorbable Braided Suture for Laparoscopic High Ligation in Rabbits.

PURPOSE: Our previous work demonstrated that intentional peritoneal injury reduces the incidence of recurrence of a patent processus vaginalis even after removal of the suture. Therefore, the necessity of permanent suture has been brought into question because of the risk of suture granuloma formation. The purpose of this study was to evaluate the efficacy of absorbable, braided versus permanent, braided suture in a rabbit survival model of laparoscopic percutaneous ligation of the processus vaginalis with intentional peritoneal injury. MATERIALS AND METHODS: Eighteen New Zealand White rabbits underwent bilateral subcutaneous endoscopically assisted ligation (SEAL) of the internal ring. Before SEAL, peritoneal injury was caused with endoscopic shears. Each animal was randomized to receive absorbable braided suture on one side and permanent braided suture on the contralateral side. The rabbits were survived for 8 weeks to allow for complete hydrolysis of the absorbable suture. Necropsy was performed during which the integrity of the repair was assessed with insufflation of carbon dioxide up to 30 mm Hg. McNemar's test for paired data was performed for statistical analysis. RESULTS: Seventeen rabbits survived 8 weeks. One rabbit died in the early postoperative period because of urinary tract obstruction. After insufflation, four (24%) recurrences were present in the absorbable group and two (12%) recurrences were present in the permanent group. This difference was not statistically significant (P = .50). Both rabbits with a recurrence on the side with permanent suture also had a recurrence with absorbable suture on the contralateral side. In all rabbits, the permanent suture was identified, whereas there was no visual evidence of absorbable suture. CONCLUSIONS: A trend toward a higher recurrence rate with the use of absorbable braided suture was present, although, in this study, the finding was not statistically significant. Caution should be used when considering implementation of absorbable suture for laparoscopic inguinal hernia repair.