A new stapler-based full-thickness transgastric access closure: results from an animal pilot trial

BACKGROUND AND STUDY AIMS

Reliable closure of the transluminal incision is the crucial step for natural orifice transluminal endoscopic surgery (NOTES) procedures. The aim of this study was to evaluate the feasibility and effectiveness of transgastric access closure with a flexible stapling device in a porcine survival model.

PATIENTS AND METHODS

We carried out four experiments (two sterile and two nonsterile) on 50 kg pigs. The endoscope was passed through a gastrotomy made with a needle knife and an 18-mm controlled radial expansion dilating balloon. After peritoneoscopy, a flexible linear stapling device (NOLC60, Power Medical Interventions, Langhorne, Pennsylvania, USA) was perorally advanced over a guide wire into the stomach, positioned under endoscopic guidance, and opened to include the site of gastrotomy between its two arms; four rows of staples were fired. One animal was sacrificed 24 hours after the procedure (progression of pre-existing pneumonia). The remaining animals were survived for 1 week and then underwent repeat endoscopy and postmortem examination.

RESULTS

Peroral delivery and positioning of the stapling device involved some technical difficulties, mostly due to the short length (60 cm) of the stapling device. The stapler provided complete leak-resistant gastric closure in all pigs. None of the surviving animals had any clinical signs of infection. Necropsy demonstrated an intact staple line with full-thickness healing of the gastrotomy in all animals. Histologic examination confirmed healing, but also revealed intramural micro-abscesses within the gastric wall after nonsterile procedure.

CONCLUSIONS

Gastrotomy closure with a perorally delivered flexible stapling device created a leak-resistant transmural line of staples followed by full-thickness healing of the gastric wall incision. Increasing the length of the instrument and adding device articulation will further facilitate its use for NOTES procedures.

Mitochondrial toxin 3-nitropropionic acid induces cardiac and neurotoxicity differentially in mice

We investigated the effects of 3-nitropropionic acid (3NPA), a previously characterized neurotoxin, in four strains of mice to better understand the molecular basis of variable host responses to this agent. Unexpectedly, we found significant cardiac toxicity that always accompanied the neurotoxicity in all strains of mice in acute and subacute/chronic toxicity testing. Caudate putamen infarction never occurred without cardiac toxicity. All mouse strains tested are sensitive to 3NPA although the C57BL/6 and BALB/c mice require more exposure than 129SVEMS and FVB/n mice. Cardiac toxicity alone was found in 50% of symptomatic mice tested and morphologically, the cardiac toxicity is characterized by diffuse swelling of cardiomyocytes and multifocal coagulative contraction band necrosis. In subacute to chronic exposure, atrial thrombosis, cardiac mineralization, cell loss, and fibrosis are combined with cardiomyocyte swelling and necrosis. Ultrastructurally, mitochondrial swelling occurs initially, followed by disruption of myofilaments. Biochemically, isolated heart mitochondria from the highly sensitive 129SVEMS mice have a significant reduction of succinate dehydrogenase activity, succinate oxygen consumption rates, and heart adenosine triphosphate after 3NPA treatment. The severity of morphological changes parallels the biochemical alterations caused by 3NPA, consistent with cardiac toxicity being a consequence of the effects of 3NPA on succinate dehydrogenase. These experiments show, for the first time, that 3NPA has important cardiotoxic effects as well as neurotoxic effects, and that cardiac toxicity possibly resulting from inhibition of the succinate dehydrogenase in heart mitochondria, contributes to the cause of death in 3NPA poisoning in acute and subacute/chronic studies in mice.

The utility of contrast-enhanced endoscopic ultrasound in monitoring ethanol-induced pancreatic tissue ablation: a pilot study in a porcine model

BACKGROUND AND STUDY AIMS

Pancreatic ablation is gaining popularity for the treatment of focal pancreatic lesions. The aim of our study was to evaluate local effects of intrapancreatic alcohol injection and the utility of contrast-enhanced endoscopic ultrasound (EUS) for its monitoring in a porcine model.

METHODS

We performed four survival experiments on 50-kg pigs. Under linear EUS guidance, 0.5 mL of 50% ethanol plus purified carbon particle solution (GI Spot) was injected into the pancreatic body to create a focal area of pancreatic necrosis. The animals survived for 24-48 hours (pigs # 1, # 2, and # 3) and 7 days (pig # 4). EUS was then repeated with and without perflutren lipid microspheres (Definity) administration through the peripheral vein. Standard and microsphere-enhanced images of the pancreas were compared. Afterwards the animals were euthanized for necropsy.

RESULTS

Alcohol injection caused focal pancreatic necrosis, which was barely seen by standard EUS as a subtle hypoechoic lesion 1 cm in diameter. Color and power Doppler EUS of this region did not reveal any blood flow. After intravenous injection of microspheres, color Doppler EUS revealed marked contrast enhancement of normal pancreatic parenchyma with a clearly delineated avascular alcohol-treated area, which on postmortem examination corresponded to the discrete necrotic area marked with carbon particles.

CONCLUSIONS

EUS-guided alcohol injection consistently causes focal areas of pancreatic necrosis. Contrast-enhanced EUS with microspheres improves visualization of altered pancreatic vascular perfusion and can be used to facilitate detection of small pancreatic lesions and its follow-up post-ablation.

Adhesion formation after peritoneoscopy with liver biopsy in a survival porcine model: comparison of laparotomy, laparoscopy, and transgastric natural orifice transluminal endoscopic surgery (NOTES)

BACKGROUND AND STUDY AIMS

Minimizing the invasiveness of operations by using natural orifice transluminal endoscopic surgery (NOTES) may reduce adhesion formation. The aim of the study was to compare rates of adhesion formation after peritoneoscopy with liver biopsy by laparotomy, laparoscopy, and transgastric NOTES.

MATERIALS AND METHODS

Experimental comparative survival study, at a university hospital. using 18 female pigs weighing 35 - 40 kg. Peritoneoscopy with liver biopsy was randomized to one of three groups: laparotomy, laparoscopy, and transgastric NOTES. Preoperative, operative, and postoperative care was standardized. Main outcome measures were: (i) survival and complication rates; (ii) assessment of adhesion formation using the Hopkins Adhesion Formation Score at necropsy (day 14).

RESULTS

100 % of pigs with laparotomy and 33.3 % with laparoscopy had adhesions compared with 16.7 % who underwent transgastric NOTES. Documented adhesion bands totals for each group were: transgastric NOTES 1; laparoscopy 4; laparotomy 17. Median adhesion formation scores were: laparotomy 2.5 (range 2 - 4), compared with laparoscopy 0.0 (0 - 2), and transgastric NOTES 0.0 (0 - 1) ( P < 0.001). Spearman coefficient analysis revealed that correlation between adhesion scores assigned by two investigators was excellent (r = 0.99, P < 0.001, 95 % confidence interval [CI] 0.9978 - 0.9996).

CONCLUSIONS

Although this was a short-term study, with a low number of animals, it showed that transgastric NOTES and laparoscopy are associated with statistically significantly lower rates of adhesion formation than open surgery when peritoneoscopy with liver biopsy is performed. Incidence and severity of adhesions were lowest with transgastric NOTES.

Zinc toxicity with pancreatic acinar necrosis in piglets receiving total parenteral nutrition

Two Hampshire-Duroc cross piglets maintained on 100% total parenteral nutrition (TPN) for 3 weeks developed pancreatic epithelial cell necrosis, diffuse acinar atrophy, and marked interstitial fibrosis. In addition, the piglets had severe villus atrophy in the small intestine as a result of TPN. Atomic absorption spectrophotometric analysis of liver samples revealed toxic hepatic zinc levels (513.5 and 491.2 ppm) in the TPN piglets (40-90 ppm in control piglets). Administering TPN bypasses homeostatic control mechanisms regulating zinc absorption at the gastrointestinal level and may reduce pancreatic secretion contributing to the accumulation of zinc in tissues. Intestinal villus atrophy, a sequela to TPN, may have also affected zinc excretion by impairing intestinal flux and desquamation. These factors should be considered in formulating TPN solutions and zinc levels administered must be reduced accordingly to avoid toxicity. Furthermore, sources and tissue levels of zinc should be investigated when necrosis, acinar atrophy, and fibrosis of the pancreas are encountered in young pigs.

Uterine Epithelioid Trophoblastic Tumour in a Red-tailed Guenon (Cercopithecus ascanius)

Epithelioid trophoblastic tumour (ETT), a rare neoplasm of chorionic-type intermediate trophoblastic cells in the human female, was diagnosed in the uterus of a red-tailed guenon, a non-human primate. The animal, having had two live births, had a recent history of heavy vaginal bleeding. Four years after the last known pregnancy, the animal developed a large invasive mass involving the uterus, right ovary and abdominal wall. The tumour was removed surgically, but at necropsy 1.5 years later was found to have a recurrent neoplasm. Histologically, the original mass consisted of nests and cords of mononuclear intermediate trophoblastic cells whose borders were accentuated by intimately associated eosinophilic hyaline extracellular proteinaceous material. Extensive coalescing areas of necrosis with mineralization surrounding islands of viable neoplastic cells created a "geographical" pattern of necrosis. Immunohistochemical examination revealed that neoplastic cells were diffusely strongly positive for cytokeratin 18, and focally positive for human placental lactogen. The histopathological and immunolabelling patterns were consistent with ETT in human beings. This is the first reported case of epithelioid trophoblastic tumour in a non-human species.

Severity of post-ERCP pancreatitis directly proportional to the invasiveness of endoscopic intervention: a pilot study in a canine model

BACKGROUND AND STUDY AIMS

Pancreatitis complicates 1% - 22% of endoscopic retrograde cholangiopancreatography procedures. The study aims were to develop a reproducible animal model of post-ERCP pancreatitis (PEP), and investigate the impact of endoscopic technique on severity of PEP.

PATIENTS AND METHODS

ERCP was carried out in six male hound dogs. Pancreatitis was induced by one of three escalating methods: 1) pancreatic acinarization with 20 - 30 mL of contrast; 2) acinarization + ductal balloon occlusion + sphincterotomy; 3) acinarization + intraductal synthetic bile injection + ductal balloon occlusion + sphincterotomy. Dogs 5 and 6 received a pancreatic stent. Necropsy was performed on postoperative day 5. All pancreatic specimens were graded by two blinded pathologists according to a validated scoring system. All dogs were compared with three control dogs.

RESULTS

Dogs 1 - 4 developed clinical pancreatitis and hyperamylasemia (11 736 vs. 722 U/L, P = 0.02). Total injury scores were significantly elevated compared with controls (6.85 vs. 1.06, P = 0.004). There was significant increase in acinar cell necrosis (0.86 vs. 0.06, P = < 0.001), and all other categories (except fibrosis) demonstrated elevated injury scores . Dogs 5 and 6 developed clinical pancreatitis without significant hyperamylasemia; total injury scores were elevated compared with controls (4.83 vs. 1.06, P = 0.01), but lower than in Dogs 1 - 4 (4.83 vs. 6.85, P = 0.25). There was escalating severity of pancreatic injury from Dogs 1 to 4 correlating with the method of endoscopic injury used.

CONCLUSION

Severity of PEP is directly proportional to invasiveness of endoscopic intervention. Pancreatic acinarization, even without balloon occlusion and sphincterotomy, can be used as a reliable animal model for future studies investigating therapy and prevention of disease.

Apoptosis has a prolonged role in the neurodegeneration after hypoxic ischemia in the newborn rat

Birth asphyxia can cause moderate to severe brain injury. It is unclear to what degree apoptotic or necrotic mechanisms of cell death account for damage after neonatal hypoxia-ischemia (HI). In a 7-d-old rat HI model, we determined the contributions of apoptosis and necrosis to neuronal injury in adjacent Nissl-stained, hematoxylin and eosin-stained, and terminal deoxynucleotidyl transferase-mediated UTP nick end-labeled sections. We found an apoptotic-necrotic continuum in the morphology of injured neurons in all regions examined. Eosinophilic necrotic neurons, typical in adult models, were rarely observed in neonatal HI. Electron microscopic analysis showed "classic" apoptotic and necrotic neurons and "hybrid" cells with intermediate characteristics. The time course of apoptotic injury varied regionally. In CA3, dentate gyrus, medial habenula, and laterodorsal thalamus, the density of apoptotic cells was highest at 24-72 hr after HI and then declined. In contrast, densities remained elevated from 12 hr to 7 d after HI in most cortical areas and in the basal ganglia. Temporal and regional patterns of neuronal death were compared with expression of caspase-3, a cysteine protease involved in the execution phase of apoptosis. Immunocytochemical and Western blot analyses showed increased caspase-3 expression in damaged hemispheres 24 hr to 7 d after HI. A p17 peptide fragment, which results from the proteolytic activation of the caspase-3 precursor, was detected in hippocampus, thalamus, and striatum but not in cerebral cortex. The continued expression of activated caspase-3 and the persistence of cells with an apoptotic morphology for days after HI suggests a prolonged role for apoptosis in neonatal hypoxic ischemic brain injury.

Refinement of canine pancreatitis model: inducing pancreatitis by using endoscopic retrograde cholangiopancreatography

The causes and treatments of pancreatitis have been studied in diverse species, but the canine pancreatitis model has been used most often due to its similarities to the condition in humans. Although pancreatitis in dogs can be induced readily by numerous methods, managing these dogs can be difficult because they often develop severe abdominal pain, vomiting, inappetance, and lethargy. In an effort to study pancreatitis, we performed a pilot study to determine whether an endoscopic pancreatic procedure would be possible in a dog and whether, through various manipulations, a new method of inducing pancreatitis could be developed. The model uses endoscopic retrograde cholangiopancreatography (ERCP), a common procedure in human gastroenterology that has been associated with postprocedural pancreatitis. Although all 8 dogs used in developing the ERCP model had both biochemical and histologic changes consistent with pancreatitis, 7 of the 8 dogs remained free of classic clinical signs of the disease. This method is presented as a refinement of a canine model and presents an alternative method of inducing pancreatitis, with decreased risk of developing associated clinical signs.