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Biomedical subjects

Theodore N Pappas

Publications and source records attributed to Theodore N Pappas.

At least 37 records · Page 2Linked to original sources
PubMed2005

Significance of histological response to preoperative chemoradiotherapy for pancreatic cancer.

BACKGROUND: Neoadjuvant (preoperative) chemoradiotherapy (CRT) for pancreatic cancer offers theoretical advantages over the standard approach of surgery followed by adjuvant CRT. We hypothesized that histological responses to CRT would be significant prognostic factors in patients undergoing neoadjuvant CRT followed by resection. METHODS: Since 1994, 193 patients with biopsy-proven pancreatic adenocarcinoma have completed neoadjuvant CRT, and 70 patients have undergone resection. Specimens were retrospectively examined by an individual pathologist for histological responses (tumor necrosis, tumor fibrosis, and residual tumor load) and immunohistochemical staining for p53 and epidermal growth factor receptor. Factors influencing overall survival were analyzed with the Kaplan-Meier (univariate) and Cox proportional hazards (multivariate) methods. RESULTS: The estimated overall survival (median +/- SE) in the entire group of patients undergoing resection was 23 +/- 4.2 months, with an estimated 3-year survival of 37% +/- 6.6% and a median follow-up of 28 months. Complete histological responses occurred in 6% of patients. Overexpression of p53 was more common in patients with large residual tumor loads. Tumor necrosis was an independent negative prognostic factor, as were positive lymph nodes, a large residual tumor load, and poor tumor differentiation. CONCLUSIONS: Histological response to neoadjuvant CRT--as measured by residual tumor load--may be useful as a surrogate marker for treatment efficacy. Characterization of the tumor cells that survive neoadjuvant CRT may help us to identify new or more appropriate targets for systemic therapy.

Adenocarcinoma↗
PubMed2005

Electroacupuncture reduces rectal distension-induced blood pressure changes in conscious dogs.

It has been shown that acupuncture relieves symptoms of abdominal pain and bloating in patients with irritable bowel syndrome (IBS). However, the mechanism of beneficial effects of acupuncture still remains unproven. The aim of the present study was to investigate the mechanisms of the antinociceptive effects of acupuncture in conscious dogs. We evaluated the increase in mean arterial blood pressure (MAP) caused by rectal distension as an index of visceral pain. Electroacupuncture (EA; 10 Hz) at ST-36 (lower leg), but not at BL-21 (back), significantly reduced the increase in MAP in response to rectal distension (30 and 40 cm3). The antinociceptive effect of EA at ST-36 was abolished by pretreatment with naloxone (a central and peripheral opioid receptor antagonist) but not by naloxone methiodide (a peripheral opioid receptor antagonist). These results suggest that EA at ST-36 may reduce visceral pain via central opioid pathway. Acupuncture may be useful to treat visceral hypersensitivity in IBS patients.

Animals↗
PubMed2005

Does resident post graduate year influence the outcomes of inguinal hernia repair?

INTRODUCTION: We evaluated the effect of the postgraduate medical education level (PGY) of surgery residents on recurrence of inguinal hernia, complications, and operative time. METHODS: Post hoc analysis was performed on prospectively collected data from a multicenter Veterans Affairs (VA) cooperative study. Men were randomly assigned to open or laparoscopic inguinal hernia repairs with mesh. Surgery residents performed repairs with designated attending surgeons present throughout all procedures. PGY level of the resident was recorded for each procedure. All patients were followed for 2 years for hernia recurrence and complications. PGY levels were grouped as follows: group I = PGY 1 and 2; group II = PGY 3; group III = PGY >/= 4; rates of recurrence, complications and mean operative time were compared. RESULTS: A total of 1983 patients underwent hernia repair. group III residents had significantly lower recurrence rates for open repairs when compared with group I (adjusted odds ratio = 0.24, 95% confidence interval [CI], 0.06, 0.997). The recurrence rate was similar among the groups for laparoscopic repair (P > 0.05) Complication rates were not different for either repair (P > 0.05). Mean operative time was significantly shorter for group III compared with group I for both open (-6.6 minutes; 95% CI, -11.7, -1.5) and laparoscopic repairs (-12.9 minutes; 95% CI, -19.8, -6.0) and between group II and group I for laparoscopic repair (-15.0; 95% CI, -24.3, -5.7). CONCLUSIONS: Despite the presence of an attending surgeon, open hernia repairs performed by junior residents were associated with higher recurrence rates than those repaired by senior residents. Lower resident level was associated with increased operative time for both open and laparoscopic repair.

Clinical Competence↗
PubMed2004

Central effect of mu-opioid agonists on antral motility in conscious rats.

Centrally applied opioids delay gastric emptying and inhibit intestinal transit. However, the mechanism of inhibitory effects of central opioids on gastric motility still remains unclear. It also remains unclear which opioid receptor (mu, delta, and kappa) stimulation affects gastric motility. We studied the central effect of opioids on antral motility in conscious rats. A strain gauge transducer was implanted on the gastric antrum to record the circular muscle contractions. The area under the curve of the antral motility, calculated as a motility index, was evaluated before and after the intracerebroventricular (icv) injection of various opioid agonists in each rat. [D-Ala2, N-Me-Phe4, Gly5-ol] enkephalin (DAMGO, 0.1-10 nmol), a mu-opioid selective agonist, significantly inhibited antral motility in a dose-dependent manner (n=4). The motility index was significantly decreased to 47.3+/-10.8% (n=4) of controls at 20 min after icv injection of DAMGO (1.0 nmol). In contrast, [D-pen2, L-Pen5] enkephalin (DADLE, 1.0 nmol), a delta-opioid selective agonist, and U50,488 (1.0 nmol), a kappa-opioid selective agonist, had no significant effects on antral motility. Pretreatment with subcutaneous guanethidine (5 mg/kg) and propranolol (1 mg/kg), but not phentolamine (1 mg/kg), significantly antagonized the inhibitory effect of DAMGO (1.0 nmol). Reduced motility index induced by DAMGO (1.0 nmol) was restored from 48.7+/-3.5% to 88.6+/-10.9% (n=5) and 80.4+/-2.2% (n=5) by guanethidine and propranolol, respectively. Our findings suggest that central mu-opioid receptor has major inhibitory effects on antral motility in conscious rats. The inhibitory effects of mu-opioid receptors are mediated via sympathetic pathways and beta-adrenoceptors.

Analgesics, Opioid↗
PubMed2004

Role of vagus nerve in postprandial antropyloric coordination in conscious dogs.

It is generally believed that gastric emptying of solids is regulated by a coordinated motor pattern between the antrum and pylorus. We studied the role of the vagus nerve in mediating postprandial coordination between the antrum and pylorus. Force transducers were implanted on the serosal surface of the body, antrum, pylorus, and duodenum in seven dogs. Dogs were given either a solid or a liquid meal, and gastroduodenal motility was recorded over 10 h. Gastric emptying was evaluated with radiopaque markers mixed with a solid meal. Dogs were treated with hexamethonium, N(G)-nitro-l-arginine methyl ester (l-NAME), or transient vagal nerve blockade by cooling. A postprandial motility pattern showed three distinct phases: early, intermediate, and late. In the late phase, profound pyloric relaxations predominantly synchronized with giant antral contractions that were defined as postprandial antropyloric coordination. A gastric emptying study revealed that the time at which gastric contents entered into the duodenum occurred concomitantly with antropyloric coordination. Treatment by vagal blockade or hexamethonium significantly reduced postprandial antral contractions and pyloric relaxations of the late phase. l-NAME changed pyloric motor patterns from relaxation dominant to contraction dominant. Solid gastric emptying was significantly attenuated by treatment with hexamethonium, l-NAME, and vagal blockade. Postprandial antropyloric coordination was not seen after feeding a liquid meal. It is concluded that postprandial antropyloric coordination plays an important role to regulate gastric emptying of a solid food. Postprandial antropyloric coordination is regulated by the vagus nerve and nitrergic neurons in conscious dogs.

Animals↗
PubMed2004

Effects of acupuncture on vasopressin-induced emesis in conscious dogs.

Although acupuncture has a significant clinical benefit, the mechanism of acupuncture remains unclear. Vasopressin, a posterior pituitary hormone, is involved in nausea and vomiting in humans and dogs. To investigate the antiemetic effects of acupuncture on vasopressin-induced emesis, gastroduodenal motor activity and the frequency of retching and vomiting were simultaneously recorded in conscious dogs. In seven dogs, four force transducers were implanted on the serosal surfaces of the gastric body, antrum, pylorus, and duodenum. Gastroduodenal motility was continuously monitored throughout the experiment. Vasopressin was intravenously infused at a dose of 0.1 U x kg(-1) x min(-1) for 20 min. Electroacupuncture (EA, 1-30 Hz) at pericardium-6 (PC6), bladder-21 (BL21), or stomach-36 (ST36) was performed before, during, and after the vasopressin infusion. To investigate whether the opioid pathway is involved in EA-induced antiemetic effects, naloxone (a central and peripheral opioid receptor antagonist) or naloxone methiodide (a peripheral opioid receptor antagonist) was administered before, during, and after EA and vasopressin infusion. Intravenous infusion of vasopressin induced retching and vomiting in all dogs tested. Retrograde peristaltic contractions occurred before the onset of retching and vomiting. EA (10 Hz) at PC6 significantly reduced the number of episodes of retching and vomiting. EA at PC6 also suppressed retrograde peristaltic contractions. In contrast, EA at BL21 or ST36 had no antiemetic effects. The antiemetic effect of EA was abolished by pretreatment with naloxone but not naloxone methiodide. It is suggested that the antiemetic effect of acupuncture is mediated via the central opioid pathway.

Acupuncture Points↗
PubMed2004

Restraint stress delays solid gastric emptying via a central CRF and peripheral sympathetic neuron in rats.

Central corticotropin-releasing factor (CRF) delays gastric emptying through the autonomic nervous system. CRF plays an important role in mediating delayed gastric emptying induced by stress. However, it is not clear whether a sympathetic or parasympathetic pathway is involved in the mechanism of central CRF-induced inhibition of solid gastric emptying. The purpose of this study was to investigate whether 1) CRF inhibits solid gastric emptying via a peripheral sympathetic pathway and 2) stress-induced inhibition of solid gastric emptying is mediated via a central CRF and peripheral sympathetic pathways. Using male Sprague-Dawley rats, CRF was injected intracisternally with or without various adrenergic-blocking agents. To investigate whether central CRF-induced inhibition of solid gastric emptying is mediated via a peripheral sympathetic pathway, rats underwent celiac ganglionectomy 1 wk before the gastric emptying study. After solid meal ingestion (90 min), gastric emptying was calculated. To investigate the role of endogenous CRF in stress-induced delayed gastric emptying, a CRF type2 receptor antagonist, astressin2-B, was intracisternally administered. Rats were subjected to a restraint stress immediately after the feeding. Intracisternal injection of CRF (0.1-1.0 microg) dose-dependently inhibited solid gastric emptying. The inhibitory effect of CRF on solid gastric emptying was significantly blocked by guanethidine, propranolol, and celiac ganglionectomy but not by phentolamine. Restraint stress significantly delayed solid gastric emptying, which was improved by astressin2-B, guanethidine, and celiac ganglionectomy. Our research suggests that restraint stress inhibits solid gastric emptying via a central CRF type2 receptor and peripheral sympathetic neural pathway in rats.

Animals↗
PubMed2004

Pancreatic duct strictures: identifying risk of malignancy.

BACKGROUND: This study aimed to define PDS characteristics that predict malignancy and would thus invoke further diagnostic evaluation or aggressive treatment. METHODS: 355 cases of PDS were diagnosed by ERCP during a 7-year period at a single institution. A retrospective review identified clinical/demographic patient data and ERCP results. RESULTS: 218 (61%) patients with a PDS were found to have an isolated PDS. Twelve percent of isolated PDS and 79% of CBD stricture-associated PDS were malignant. The sensitivity and specificity for the double duct sign for malignancy were 77% and 80% respectively, and the positive predictive value was 65%. Predictors of malignancy were statistically similar for both isolated PDS and those associated with a CBD stricture. Univariate predictors of malignancy included stricture location in the pancreatic head/neck, jaundice, and patient age. Predictors of benign disease included a history of pancreatitis, the presence of multiple strictures, pancreatic duct stones, pseudocyst, pancreas divisum anatomy, irregular side branches, and irregular pancreatic duct morphology. Less than 1% of patients with either pancreas divisum anatomy, pancreatic duct stones, or pancreatic pseudocyst had malignancy. Using malignancy as the dependent variable, multivariate factors included in the final prognostic equation were history of pancreatitis (odds ratio 0.009 with history of pancreatitis), stricture location in the head or neck (odds ratio 42) and irregular pancreatic duct side branches (odds ratio 0.05 with irregular branches). CONCLUSIONS: This study demonstrates that certain characteristics of PDS can predict the subset of patients who have an increased risk of cancer.

Algorithms↗
PubMed2004

Reducing hospital morbidity and mortality following esophagectomy.

BACKGROUND: Esophagogastrectomy (EG) is a formidable operation with significant morbidity and mortality rates. Risk factor analyses have been performed, but few studies have produced strategies that have improved operative results. This study was performed in order to identify prognostic variables that might be used to develop a strategy for optimizing outcomes after EG. METHODS: The records of all patients (n = 379) who underwent EG patients at a tertiary medical center between 1996 and 2002 were retrospectively reviewed. Thirty-day morbidity and mortality were determined, and multivariable logistical regression analysis assessed the effect of preoperative and postoperative variables on early mortality. RESULTS: Operations included Ivor Lewis (n = 179), transhiatal (n = 130), and other approaches (n = 70). Operative mortality was 5.8%; 64% experienced complications, including respiratory complications (28.5%), anastamotic strictures (25%), and leak (14%). Increasing age, anastomotic leak, Charlson comorbidity index 3, worse swallowing scores, and pneumonia were associated with increased risk of mortality by univariate analysis. However, only age (p = 0.002) and pneumonia (p = 0.0008) were independently associated with mortality by multivariable analysis. Pneumonia was associated with a 20% incidence of death. Patients with pneumonia had significantly worse deglutition and anastomotic integrity on barium esophagogram compared with patients without pneumonia (p < 0.001, Mann-Whitney rank sum test). CONCLUSIONS: Morbidity and mortality of EG are significant, but most complications, including anastomotic leak, are not independent predictors of mortality. The most important complication after EG is pneumonia. Strategies to decrease postoperative mortality should include careful assessment of swallowing abnormalities and predisposition to aspiration by cineradiography or fiberoptic endoscopy. After EG, acceptable pharyngeal function and airway protection should be verified before resuming oral intake.

Adenocarcinoma↗
PubMed2004

Clinical application of porcine small intestinal submucosa in the management of infected or potentially contaminated abdominal defects.

The repair of abdominal wall defects in potentially contaminated or grossly infected fields presents a difficult clinical problem. Polypropylene mesh is relatively contraindicated in these settings because of the potential for chronic infection. The alternatives to polypropylene include polyglactin mesh, which is not associated with chronic infection but is associated with a 100% recurrence of hernia. The ideal prosthetic for this patient group should be resistant to infection and ensure a low rate of hernia recurrence. We studied the use of small intestinal submucosa, which has been reported to be resistant to infection and incorporates into the fascia over 3 to 6 months, in 20 patients with ventral or inguinal hernias (18 ventral, 2 inguinal hernia) in the setting of bacterial contamination. The early postoperative complication rate was 50%. One patient with fasciitis had degradation of the small intestinal submucosa and loss of the bioprosthesis within 7 days. Other early complications included seroma (n=2), ileus (n=1), and wound infection (n=8). No patient experienced chronic infection. Mean follow up was 15.7 months and the rate of recurrence documented by CT or physical examination was 30%. We concluded the following: (1). small intestinal submucosa is an effective alternative bioprosthesis in the management of ventral/inguinal hernia when there is associated bacterial contamination; (2). human vs. pig immune response has not been seen in this patient population; (3). early graft failure due to overwhelming fascial infection was noted in one patient and may be a limitation of this technology in a minority of patients; and (4). early hernia recurrence is relatively low but long-term follow-up has not been completed.

Abdominal Wall↗
PubMed2004

Laparoscopic Nissen fundoplication for treating reflux in lung transplant recipients.

Gastroesophageal reflux disease may contribute to pulmonary injury and the development of bronchiolitis obliterans syndrome in lung transplant patients. As a result, such individuals are increasingly likely to undergo corrective gastrointestinal surgery. The present study collected outcome data for 28 lung transplant patients with documented reflux who underwent an uncomplicated laparoscopic Nissen fundoplication at our institution. The results were compared to data from 63 nontransplant reflux patients who had undergone the procedure over the same time period. All Nissen fundoplications were conducted by the same surgeon. There were no intraoperative or perioperative deaths in either patient group. Operative parameters did not differ but the postoperative hospital stay was significantly greater for the lung transplant patients (P<0.05). Seven transplant patients (25%) were readmitted within 30 days compared to two readmissions (3.2%) in the reflux group. Five transplant patients (17.9%) have died, all from pulmonary complications; on average, death occurred 15.5 months after the Nissen surgery. There have been no deaths in the reflux group. These data indicate that laparoscopic Nissen fundoplication can be performed on lung transplant recipients to treat reflux. The average hospital stay is longer and there are more frequent readmissions in this population, but this does not appear to be due to any Nissen-related morbidity.

Adult↗
PubMed2004

European surgical survey of acute pancreatitis--union of diversity.

The widely variable nature of acute pancreatitis renders it a challenging disease to manage via standardized approaches. King and Siriwardena present their findings from a survey of European surgical approaches to diagnostic and therapeutic management of severe acute pancreatitis in an attempt to delineate areas of discordance that may help direct future studies. An erratic trend in the management of severe acute pancreatitis is evident despite growing evidence to support several diagnostic and therapeutic procedures as standards of care. On the other hand, areas of discordance largely characterize those currently lacking in adequate literature support underscoring the need to generate randomized studies that will address them.

Acute Disease↗