Background. Sleep deprivation as a result of in-house night call may alter capacity to learn. Surgical residents and medical students, in both sleep-deprived and rested states, read surgical journal articles and later answered questions regarding their content as a measure of ability to learn while participating in scheduled night call.Methods. Medical students (n = 35) and residents (n = 21) rotating on surgical services kept logs of hours slept during a 4-week study period. Subjects read six selected articles at separate early morning sittings during weeks 1 and 3. A multiple choice test was given 1 week after each session to assess short-term recall, and all tests were given again 3 months later to assess retention of information over the longer term. Scores were compared with the sleep data. Subjective measures of fatigue and motivation elicited from subjects also were evaluated.Results. Sleep deprivation (4 hours or less uninterrupted sleep per night) resulted in increased fatigue and decreased motivation among medical students and residents (p < 0.05, t test). Objective scores on tests administered 1 week and 3 months after reading did not show an effect attributable to sleep deprivation (p > 0.05, t test).Conclusions. Sleep deprivation leads to subjective feelings of increased fatigue and decreased motivation. Residents and medical students, however, whether sleep deprived or not, obtain comparable scores on objective tests measuring both short-term and long-term retention of newly learned material. The ability to learn medically relevant information does not appear to be significantly altered by the degree of sleep deprivation associated with clinical rotations on surgical services.

We investigated the role of the vagi in modulation of colonic motor activity in the fasted and fed states and determined the extent of vagal influence on colon motility in conscious monkeys. Monkeys were implanted with force transducers on the colon. A vagal cooling chamber was implanted supradiaphragmatically, and a vagal stimulating electrode was implanted just distal to the chamber. One week was allowed for recovery. After an overnight fast, control recordings were made for 1 h, and then the monkeys were either fed or remained fasting, with or without adrenergic blockade (propranolol and phentolamine). Then while recordings continued the vagi were cooled to their predetermined denervation temperature for 1 h. In a second set of experiments, adrenergic blockers were injected, and the vagi were stimulated during vagal cooling with or without atropine administration. In both the fasted and fed states, the contractile frequency was decreased during vagal cooling, with or without adrenergic blockade. With adrenergic blockade, however, the frequency of colon contractions was greater during cooling than during cooling without such blockade. Inhibition of colonic contractions during cooling decreased in magnitude from the proximal to the distal colon. Vagal efferent stimulation increased contractile frequency at all sites, but after atropine it decreased contractile frequency. We conclude that the vagi have either a direct or indirect influence on fasting and fed colonic motor activity throughout the colon, and that a nonadrenergic, noncholinergic inhibitory pathway is under vagal control.

Sympathetic stimulation during and after laparotomy and other surgical procedures may be a factor inducing postoperative ileus. In experiments conducted in fasting monkeys, the effects of the selective sympathetic agonists alpha-1 (phenylephrine), alpha-2 (ST-91), beta-1 (dobutamine), and beta-2 (terbutaline) on colon contractile activity were measured. Strain gauges were implanted on the colon. Recordings were made for 1 hour (control) and then for an additional hour during continuous infusion by one of a range of doses of each drug (experimental). The drug doses were chosen to cover both physiologic and pharmacologic concentrations. All of the sympathetic agonists caused a dose-dependent decrease in the frequency of colon contractions. The beta-agonists did so at a concentration that is sufficiently low to support a hypothesis that beta-stimulation leading to inhibition of smooth-muscle contraction may play an important role in the genesis of postoperative ileus.

Postjunctional interactions of histamine and methacholine were defined by measuring contraction of intact strips of circular smooth muscle.Concentration-response curves to histamine were obtained with and without a threshold concentration (30 nM) of methacholine present.Methacholine increased the maximum response to histamine and shifted the concentration-response curve to the left.The increased response was greater than the additive effect of methacholine plus histamine.Because agonist-activation of protein kinase C might modulate gastrointestinal smooth muscle contraction we also tested the ability of phorbol dibutyrate (PDB) to potentiate contraction.Circular muscle was pretreated 20 min with 0.1 uM PDB, then stimulated with histamine or methacholine.Contractions were potentiated at all concentrations of histamine and at the lower concentrations of methacholine.The maximum response to histamine increased significantly, but the maximum response to methacholine did not.The mechanism of potentiation was then investigated by determining whether agonists and activation of protein kinase C could potentiate Ca'+-induced contraction of staphylococcal a-toxin permeabilized fibers.Ca2+induced contractions were potentiated by histamine (100 PM), methacholine (100 NM), GTP-y-S (100 PM) and 0.1 uM PDB.In intact muscle, carbachol (0.1 -10 PM) and PDB (0.1 and 1 PM) increase protein kinase C activity and cause translocation from cytosolic to membrane-bound forms (Zhang and Buxton, FASEB

The phenomenon of bacterial translocation, the movement of viable indigenous microorganisms across the intestinal epithelial barrier, has been recognized for almost 100 years. At the present time, the precise mechanism of microbial transport is unknown. Active epithelial uptake and phagocyte-mediated transport have been proposed as likely explanations for the extraintestinal movement of bacteria to mesenteric lymph nodes and distant organ sites. Translocation has been proposed as the pivotal process associated with intestinal origin portal sepsis in seriously ill and immunocompromised patients. While several etiologic factors can be implicated in the pathogenesis of bacterial translocation, the present clinical implications are based almost solely on studies of dogs, rats and mice. Present investigations continue to suggest a causal relationship between intestinal mucosal integrity and infection by indigenous gastrointestinal bacteria.

In this study, we investigated the nature of, and mechanisms underlying, altered smooth muscle function in the inflamed jejunum of Zsoiralis-infected CD1 and nude fice.Infection was accompanied by inflammation in the Jejunum, as illustrated by a 3-fold increase in myeloperoxidase (MPO) activity.Isometric tension was recorded from lcm jejunal segments ofiented in the longitudinal axis and studies were performed on noninfected control mice or on mice 6 days post-infection.Carbachol (lOnM-0.1&l)caused a concentrationdependent increase in tension in control and infected CD1 mice, but the maximum increase in carbachol-induced contraction was approximately 100% greater in infected CD1 mice.In addition, the response to substance P (l&4) was 103% greater in infected CD1 mice compared to controls.

The diagnosis of carcinoma in the esophagus routinely leads to surgery so that the development of expert systems which reduce diagnostic uncertainty is useful. Herein we quantify the histological features of esophageal tissue with microscopic image analysis (MIA) which facilitates statistical analysis and expert system development. Statistical discriminant analysis of MIA data is used to produce a model which delineates high or low survival in patients with esophageal adenocarcinoma. Based on this model, rule-based expert systems, application programs and example-based neural networks are compared. Each provides a useful risk assessment for patient survival after surgery on a training-test case set of esophageal adenocarcinoma.

Microscopic Image Analysis (MIA) was applied to quantify nuclear features in adenocarcinoma of the esophagus. It was found that rotation of the axis in the bivariate relation between total optical density (OD) of nuclear DNA and nuclear area corrected the effects of sectioning in this tissue. A stepwise discriminate model was developed which identified high and low survival in patients dependent on MIA measurements of nuclear area, total OD, average OD and texture of nuclear DNA.

Sympathetic hyperactivity has been implicated as an etiologic factor in postoperative ileus. The effects of methoxamine (alpha-agonist) and isoproterenol (beta-agonist) on colon contractions and blood flow were studied in nine monkeys. Phentolamine (alpha-antagonist) and propranolol (beta-antagonist) were used to block the effects of the appropriate agonist. Methoxamine caused a dose-related inhibition of colon contractions and a decrease in inferior mesenteric artery (IMA) blood flow. Isoproterenol caused a dose-related inhibition of colon contractions and an increase in IMA blood flow. The contractile and blood flow effects of methoxamine were blocked by phentolamine and those of isoproterenol by propranolol. Mechanical reduction of IMA blood flow by an amount equivalent to that observed with the highest dose of methoxamine caused no change in contractions in the segment of colon supplied by the IMA. Both alpha- and beta-agonists inhibit colon contractions and have the expected effects on IMA blood flow. The contractile and blood flow responses of the agonists can be blocked by appropriate antagonists. The blood flow changes are not responsible for the contractile changes. These results indicate that sympathetic hyperactivity may play a role in postoperative ileus.

A retrospective study of 86 patients with carcinoid tumors was undertaken covering an 18-year period. The most common sites of tumor were the jejunoileum (28 cases), appendix (22), and rectum (16). These were followed by the bronchus, duodenum, colon, and stomach. Three tumors had such wide-spread metastasis that their primary sites of origin could not be determined. The appendiceal and rectal carcinoids were often benign and usually found as incidental tumors, whereas colon and jejunoileal carcinoids were often metastatic. The jejunoileal carcinoids were commonly associated with multiple tumor sites and had a high frequency of secondary neoplasms. Symptomatic tumors were often metastatic. Chronic intermittent intestinal obstruction was often present with mesenteric metastasis, and liver metastasis was associated with the carcinoid syndrome. The patients' survival was good if aggressive surgical therapy was undertaken for palliation of the tumors.

A five-year surgical would surveillance program included the following features: (1) observations were made by a trained nurse-surveyor; (2) all surgical services, without exception, were surveyed; (3) the nurse-surveyor reported directly to the Chief, Surgical Service; (4) all infected wounds and all suspected of harboring an infection were observed daily by the nurse-surveyor; (5) all wounds were inspected on the third and seventh postoperative days, at hospital discharge, and at a follow-up clinic visit; and (6) cultures were obtained from all infected wounds. Data concerning infections for all surgical services were published each month at the mortality-morbidity conference. The number of wounds closed primarily and the number of infected wounds were recorded, together with calculations of wound infection rates by operation class, for each surgical service and for the whole hospital. During the study, the rate of wound infections progressively declined. The overall incidence decreased from 3.5% before the study began to less than 1% at its conclusion.

A predictable and progressive experimental intestinal obstruction, simulating a malignancy but without neoplastic change has been produced by application of a silicone rubber ring around the bowel of 20 rats, seven dogs, and five monkeys. Serosal reaction produced fibrous tissue that resulted in an "apple core" obstruction. An easily assembled extraluminal balloon device of silicone rubber can be used to produce acute and progressive experimental obstruction, especially of the large bowel.