Sizing, stoichiometry and optical absorbance variations of colloidal cadmium sulphide nanoparticles.

Simple preparative methods were used to synthesise cadmium sulphide particles in the size ranges larger than those associated with quantum confinement. UV/visible absorption spectra were measured. Rayleigh and Mie theories were used to analyse normalised absorption spectra to allow estimates of particle size and number to be obtained simultaneously. Each model was utilised in an appropriate size and wavelength range. Surprisingly, Mie calculations were found to over-estimate the absorbance of particles below 50 nm radius. Powder X-ray diffraction results showed the crystallites to be independent of particle size and suggested that the particles grew through aggregation of smaller bodies. The Mie results could therefore be interpreted in terms of changes in the particles' optical indicatrix with radius. Large poly-crystalline particles (>50 nm radius) should possess a near spherical indicatrix, fulfilling the assumptions of the Mie theory. The indicatrix of particles smaller than 50 nm should become increasingly anisotropic with decreasing size, leading to discrepancies between the Mie model and measured data. Although the results could also be explained through changes in the magnitude of the particle refractive index, compositional (Auger electron spectroscopy, energy dispersive X-ray analysis) and structural (powder X-ray diffraction) analyses of the particles complicate the hypothesis. Energy dispersive X-ray results showed that small cadmium sulphide particles possessed a large excess of sulphur suggesting a change in effective cadmium sulphide stoichiometry.

Indispensable benefits and unavoidable costs of unattended sound for cognitive functioning.

Critical to survival, and also to the organism's efficient management of the flow of information in the brain, is attentional selectivity; the ability to select one source of information to guide action whilst ignoring others that are irrelevant to the current behavioural goal. But such selectivity is not merely the inclusion of the relevant information and the complete neglect of irrelevant information. We discuss in this paper the way that all sound is processed in an obligatory fashion--whether relevant or irrelevant--and discuss the fate of sound in the case when it is irrelevant to the immediate mental task. Using the so-called irrelevant sound paradigm we show that unattended information is both registered and organised. This obligatory process of organisation compromises the efficiency of particular types of mental activity. We discuss how such interference comes about but the key emphasis is upon the possible beneficial effects of such processing-of-the-irrelevant, in allowing the switching of attention to be more facile and intelligent and in allowing the accumulation of evidence about statistical regularities in the auditory world (such as those helpful to the efficient perception, acquisition and use of language). In sum, we describe how purposeful processing based on directed attention is in a state of tension with the obligatory, automatic processing of the unattended. One of the consequences of this tension is typically manifested in auditory distraction, but the benefits of processing of the attended may considerably outweigh this disadvantage.

Ethanol self-administration in freely feeding and drinking rats: effects of Ro15-4513 alone, and in combination with Ro15-1788 (flumazenil).

Recent work in our laboratory demonstrated that Ro15-4513, a partial inverse benzodiazepine (BDZ) agonist, decreases ethanol (ETOH) self-administration in rodents under fluid deprivation conditions. The present study further examined the effects of Ro15-4513 (2.5 and 5.0 mg/kg) alone and in combination with Ro15-1788, (flumazenil) (8.0 and 16.0 mg/kg), a BDZ receptor antagonist on ETOH self-administration in freely feeding and drinking rats. Animals were trained to consume ETOH (11% v/v) using a limited access procedure. Measurements were taken at 10- and 60-min intervals. Ro15-4513 (2.5 and 5.0 mg/kg) markedly attenuated ETOH consumption at both intervals. The antagonistic actions of Ro15-4513 were completely blocked by the higher dose of flumazenil at both intervals; the lower dose failed to antagonize the Ro15-4513-induced reduction of ETOH intake. When flumazenil was given alone, both doses reduced ETOH self-administration at 60 min; although the magnitude of the antagonism was comparable to that of Ro15-4513 only with the highest does of flumazenil (16.0 mg/kg). Neither Ro15-4513 nor flumazenil alone or in combination significantly altered water intake at any of the tested doses. Rats pretreated with Ro15-4513 showed a substantial reduction in blood ethanol concentration (BEC) compared with the Tween-80 vehicle condition at the 10-min interval. However, the BEC of animals given Ro15-4513 in combination with flumazenil were similar to rats given Tween-80 vehicle. The present study extends our previous research by demonstrating that Ro15-4513 and flumazenil attenuate ETOH self-administration in non-food or water deprived rats.(ABSTRACT TRUNCATED AT 250 WORDS)

The use of prosthetic stents in tracheobronchial, gastrointestinal, and genitourinary diseases.

The concept of using a stent to maintain patency of a lumen is not new. As early as 1969, stents were being investigated in the peripheral arterial system as a means of preventing restenosis after dilatation by balloon angioplasty (Dotter, 1969). Since then, numerous reports have demonstrated the use of stents in both the peripheral and coronary artery systems (Maass et al., 1982; Dotter et al., 1983; Wright et al., 1985; Palmaz et al., 1987). Concomitant with the investigation of expandable endovascular metal prosthesis has been the development of prosthetic devices for management of tracheobronchial, gastrointestinal, and genitourinary diseases. We will review the use of endoscopically placed prosthetic devices in the management of diseases affecting these systems.

Imaging of complications of laparoscopic cholecystectomy.

Laparoscopic cholecystectomy has gained widespread acceptance for treatment of cholelithiasis. Because radiologists have a primary role in recognizing and treating complications of this surgical technique, we reviewed the clinical records and imaging studies of 29 patients with complications after laparoscopic cholecystectomy. Complications included bile duct injuries (15 cases), retained common bile duct stones (seven cases), cystic duct stump leak (four cases), bowel perforation (two cases), abdominal abscess (two cases), intraperitoneal gallstones (2), and failure to diagnose malignant bile duct obstruction (one case). Twenty-two patients required reoperation, and one patient with bowel perforation died. Eleven of 15 bile duct injuries were imaged prior to hepaticojejunostomy. Nine of 11 were proximal bile duct injuries within 2 cm of the junction of the right and left bile ducts. Endoscopic retrograde cholangiography (ERC) identified the distal extent of injuries, but transhepatic cholangiography (THC) was necessary to fully evaluate the proximal extent of the bile duct abnormalities. ERC was used for diagnosis and treatment of the seven patients with choledocholithiasis. Abdominal films showed intraperitoneal in one patient with bowel perforation, intraperitoneal stones in a second patient, and intraabdominal abscess in one of two patients in whom abdominal films were performed. Computed tomography (CT), done in three patients with bowel perforation or abscess, showed the one duodenal perforation, and the two abscesses. CT also showed bilomas, intraperitoneal gallstones, and unsuspected malignancy. Imaging studies detected and defined complications after laparoscopic cholecystectomy in all cases.

Acute gastrointestinal bleeding. Experience of a specialized management team.

The initial experience of a specialized management team organized to provide expedient care for all acute major gastrointestinal bleeding in protocolized fashion at a large referral center is presented. Of the 417 patients, 56% developed bleeding while hospitalized. Upper gastrointestinal bleeding accounted for 82%. The five most common etiologies included gastric ulcers (83 patients), duodenal ulcers (67 patients), erosions (41 patients), varices (35 patients), and diverticulosis (29 patients). Nonsteroidal anti-inflammatory drugs were implicated in 53% of gastroduodenal ulcers. The incidence of nonbleeding visible vessels was 42% in gastric and 54% in duodenal ulcers. The rates of rebleeding were 24% (20 patients) in gastric ulcers and 28% (19 patients) in duodenal ulcers. Predictive factors for rebleeding included copious bright red blood, active arterial streaming, spurting, or a densely adherent clot. The rebleeding rate for esophagogastric varices was 57%. The mortality rate overall was 6% (27 patients), with rates varying from 3% (five patients) for gastroduodenal ulcers to 40% (14 patients) for esophagogastric varices. The morbidity rate for the entire patient population was 18% (77 patients), dominated by myocardial events (34 patients). The average length of hospitalization for gastroduodenal ulcers was 5 days, for diverticulosis 8 days, and for varices 10 days. The major efforts of a specialized Gastrointestinal Bleeding Team would be best directed at both reducing the morbidity associated with acute bleeding and reducing the overall cost of care.

An unusual case of myxedema megacolon with features of ischemic and pseudomembranous colitis.

Myxedema megacolon is rare; usually, it manifests with abdominal distention, flatulence, and constipation. Herein we describe a 72-year-old man who had intermittent diarrhea, bloating, and abdominal pain for more than a year. Cultures of stool specimens for Clostridium difficile enterotoxin were variably positive and negative. Colonoscopic biopsy specimens were thought to be consistent with chronic ischemia. Thyroid function tests showed severe hypothyroidism; the patient's symptoms resolved with thyroid hormone replacement. We hypothesize that gross dilatation of the colon, attributed to myxedema, was followed by intestinal ischemia and complicated by recurrent episodes of pseudomembranous colitis. A review of the relevant literature is provided. This unusual manifestation of myxedema should be considered in the differential diagnosis when a patient has diarrhea, bloating, and abdominal pain.

Treatment of benign esophageal stricture by Eder-Puestow or balloon dilators: a comparison between randomized and prospective nonrandomized trials.

To determine whether the natural history of strictures is affected by the type of dilator used to treat newly diagnosed peptic strictures, we designed a prospective randomized trial to compare the results after Eder-Puestow or Medi-Tech balloon dilation. We entered 31 patients into the trial. We also prospectively followed up all 92 nonrandomized patients who underwent their first dilation for a benign stricture during the same period as the prospective randomized trial. The nonrandomized patients also underwent dilation with either the Eder-Puestow or the balloon technique at the discretion of the gastroenterologist performing the endoscopy. We found no statistically significant differences in the immediate or long-term results of the two methods among the randomized, nonrandomized, and overall combined groups. All but 1 of the 123 patients had immediate relief of dysphagia. Within each group of patients, the probability of remaining free of dysphagia 1 year after the initial dilation was approximately 20%, and the probability of not requiring a second dilation was approximately 65% with either technique. Major (esophageal rupture) and minor (bleeding or chest pain) complications occurred in 1% and 5% of the patients and 0.4% and 3% of the total dilation procedures, respectively. The esophageal rupture and four of six minor complications occurred after repeated dilations. Five of the six minor complications occurred with use of the Eder-Puestow dilators. We conclude that Eder-Puestow and balloon dilations of benign esophageal strictures are associated with similar outcomes, but repeated dilations and the Eder-Puestow technique may be associated with an increased risk of complications.

Persistent bile leak after liver transplantation: biloma drainage and endoscopic retrograde cholangiopancreatographic sphincterotomy.

Persistent bile leaks after liver transplantation were successfully treated in three patients with percutaneous or surgical drainage of bilomas and endoscopic retrograde ampullary sphincterotomy. In all three patients, biliary anastomoses were achieved by means of choledochocholedochostomies, with a T-tube stent in the anastomosis. The bile leaks led to subhepatic bilomas that had persistently high catheter outputs (greater than 200 mL per 24 hours) for longer than 1 month. Biloma drainage decreased shortly after sphincterotomy.

Rheology of acrylic denture-base polymers.

The aim of this study was to investigate the changing rheological behavior of a denture-base polymer from mixing to setting. In addition, monomer evaporation and exothermic behavior of the mix were evaluated. The results show that the material behaves as a pseudoplastic fluid. It is shown that the viscosity increases at different rates with respect to lapsed time, and increases with higher temperature. Also, it is shown that polymerization and monomer evaporation both play a part in dough formation.

Anatomic, motor, and clinical assessment of vertical banded gastroplasty.

The aim of this study was to assess gastric anatomy, motility, and emptying after vertical banded gastroplasty and to correlate the anatomic and physiologic results with clinical outcome. Eleven patients were studied at least 7 mo after operation, by which time they had lost 31% +/- 4% (mean +/- SEM) of their excess body weight. Stomal diameter, volume, and distensibility of the proximal gastric pouch were determined by a balloon distention technique. Gastric emptying was monitored scintigraphically both with and without distention of the proximal pouch. Stomal diameters ranged from 10 to 15 mm (mean +/- SEM = 11 +/- 1 mm), and pouch capacity ranged from 20 to 150 ml (76 +/- 9 ml). Mean intrapouch pressure was 13 mmHg before distention, increased to 22 mmHg with distention to half-maximal capacity, and then changed little with further distention to maximum capacity. Near maximal pouch distention during gastric emptying of a 300-ml test meal decreased antral contractile activity and speeded the initial rate of emptying (t25 with distention = 14 +/- 3 min vs. 24 +/- 3 min without distention, p less than 0.03), but did not alter the later rate of emptying. No clear-cut relationship was present between weight loss and stomal diameter, pouch volume, or gastric emptying. The conclusion was that distention of the proximal gastric pouch created by vertical banded gastroplasty inhibited antral contractions and increased the initial rate of gastric emptying, but no clear-cut correlation was found in this cohort between weight loss after the operation and stomal diameter, pouch size, and gastric emptying.

Transesophageal echocardiography: technique, anatomic correlations, implementation, and clinical applications.

The introduction of transesophageal echocardiography has provided a new acoustic window to the heart and mediastinum. High-quality images of certain cardiovascular structures [left atrial appendage, thoracic aorta, mitral valvular apparatus, and atrial septum] can be obtained readily (average examination, 15 to 20 minutes). In this article, we discuss the technique of image acquisition, image orientation, and anatomic validation. In addition, we describe our experience with the first 100 awake patients who underwent transesophageal echocardiography at our institution. The procedure was well accepted by the patients and associated with no major complications. The clinical indications for this procedure have included thoracic aortic dissection, prosthetic cardiac valve dysfunction, detection of an intracardiac source of embolism, endocarditis, cardiac and paracardiac masses, and mitral regurgitation. Transesophageal echocardiography also proved to be useful in assessment of critically ill patients in whom standard transthoracic echocardiographic images did not provide complete assessment. In these patients (who had extensive chest trauma, had undergone an operation, or were in an intensive-care unit), rapid assessment of the cardiovascular status at the bedside was possible with transesophageal echocardiography. On the basis of our initial experience, we conclude that transesophageal echocardiography complements standard two-dimensional Doppler and color flow examinations and will considerably improve the care of patients with cardiovascular disorders by providing high-quality unique images.

Intragastric balloons in comparison with standard therapy for obesity--a randomized, double-blind trial.

Intragastric balloons are new but commonly used devices for the treatment of obesity; however, their safety and efficacy have not been established. We report our results of a small, double-blind, randomized trial in which the effectiveness of intragastric balloons was compared with that of conventional medical therapy for obesity. Twenty-two patients, who were 21 to 77% over ideal body weight, were studied. Eleven underwent insertion of an intragastric balloon, and 11 underwent sham procedures. One patient with a gastric balloon withdrew from the study after 3 days. Weight loss at 2 to 3 months in the conventional therapy group averaged 2.8 kg; in the balloon-treated group, the mean weight loss was 5.8 kg (P greater than 0.15). Of the 10 balloons, 8 spontaneously deflated, and 1 was passed in the stools. We noted gastric erosions in five patients and multiple gastric ulcers in one. We conclude that the intragastric balloon was not clearly effective in inducing weight loss, had a high rate of spontaneous deflation, and was damaging to the gastric mucosa. Controlled trials should be done before similar weight-reduction devices are used in routine clinical practice.

Barium-impregnated fibrin glue: application to a bleeding duodenal sinus.

A 64-year-old man with Crohn's disease who had undergone repair of an ileovesical fistula and ileoileostomy had numerous postoperative complications related to sepsis and wound healing. Subsequently, upper gastrointestinal bleeding developed, and the site was identified as a duodenal sinus. Medical management was unsuccessful in controlling the bleeding. Because of the considerable risk associated with reoperation in this seriously ill patient, approval was obtained from the Food and Drug Administration to use fibrin glue in an attempt to prevent further bleeding. The glue was mixed with barium and placed in the duodenal sinus under endoscopic guidance. The barium-impregnated glue facilitated follow-up surveillance with abdominal roentgenography. The patient had no further gastrointestinal bleeding. Further clinical and experimental studies should be conducted to determine the mechanism of action and the efficacy of this application of fibrin glue.

Balloon dilatation of upper digestive tract strictures.

The results of balloon dilatation of upper digestive tract stricture in 111 patients were evaluated. Eighty-eight patients had esophageal strictures and 23 had gastric or pyloric strictures. Thirty-six patients had strictures associated with previous operations. Twenty-two percent of the patients with esophageal strictures had malignancies. Overall, 92% were successfully dilated, with a complication rate of 3%. Follow-up information was available in 95% of patients. Eighty-seven percent of living patients experienced symptomatic improvement, which lasted for a median period of 12 mo. Forty percent required a further procedure during the period of follow-up. We found no difference between esophageal strictures and gastric or pyloric strictures in success rate, complications, or need for further dilatation, although patients with esophageal strictures were more apt to have symptomatic improvement. Postoperative strictures responded as well as nonoperative strictures. Previously dilated strictures in patients with esophageal reflux were managed as successfully as strictures never before dilated. We found balloon dilatation of upper digestive tract stricture to be a safe, effective technique.