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Biomedical subjects

F E Silverstein

Publications and source records attributed to F E Silverstein.

82 records · Page 5Linked to original sources
PubMedDate not supplied

Morphological consequences of bisacodyl on normal human rectal mucosa: effect of a prostaglandin E1 analog on mucosal injury.

Bisacodyl causes acute injury to the human rectal mucosa. Our objectives were to test whether pretreating the human rectum with an enema of 400 micrograms of a prostaglandin E1 analog (misoprostol) would ameliorate the mucosal injury provoked by an enema of 10 mg of bisacodyl, and to follow the evolution of the bisacodyl-induced injury in normal volunteers. Mucosal biopsies were taken 10 cm from the anus with an endoscopic forceps through a straight sigmoidoscope. Histological sections were interpreted blindly. In a preliminary experiment without bisacodyl, biopsies obtained from six subjects after misoprostol administration were indistinguishable from those taken from another six subjects after enemas of saline. In a parallel treatment experiment involving 30 subjects, all subjects sustained injury to the superficial epithelium and upper third of the crypt within 30 min after bisacodyl. Pretreatment with misoprostol also failed to prevent deeper injury to the lower third of colonic crypts. In a cross-over trial, a subset of four volunteers had biopsies at five different intervals after an enema of bisacodyl or saline. For up to 30 hours after bisacodyl, there was histological evidence of mild inflammation. Bisacodyl-induced colitis might confound the assessment of patients with suspected inflammatory bowel disease.

Administration, Topical↗
PubMedDate not supplied

Endoscopic ultrasound probes.

Ultrasound probes are being developed as alternatives to dedicated ultrasound endoscopes. These probes have been designed to pass through the instrument channel of ordinary fiberoptic or video endoscopes. We have developed a 20-MHz mechanical linear probe for use within the upper gastrointestinal tract, pancreatic duct, biliary tree, and colon. Rotational mechanical sector scanning probes as well as phased array probes are also being developed. Ultrasound probes are best used for high resolution imaging of focal endoscopically visible lesions. Endoscopic visualization enables direction of the probe to the lesion of interest. Unlike dedicated ultrasound endoscopes, ultrasound probes do not screen large areas of tissue and do not have deep penetration. Ongoing research will help define the indications for use of these probes and should lead to further refinements in their design.

Animals↗
PubMedDate not supplied

The effects of applied pressure on the thickness, layers, and echogenicity of gastrointestinal wall ultrasound images.

Endoscopic ultrasound imaging of the gastrointestinal wall can be performed through intraluminal fluid or by direct transducer contact with the wall. We tested the hypothesis that the ultrasound appearance of the gastrointestinal wall is influenced by the amount of pressure applied when the transducer is in contact with the tissue. Fresh autopsy specimens from the porcine gastrointestinal tract were examined in vitro using an 8.5-MHz linear array ultrasound system. As transducer pressure against the wall was increased from 0 to 10 KPa, changes were seen on the images in wall thickness, tissue echogenicity, and the number of layers. The stomach and rectum were more resistant to compression than the esophagus, duodenum, and colon. Wall echogenicity increased with increasing degrees of applied pressure and some layers were obliterated by this pressure. The second ultrasound layer, or deep mucosa, appeared to be the most susceptible to compression. Endoscopic ultrasound imaging artifacts should be reduced by limiting the amount of pressure applied to the wall with the transducer.

Animals↗
PubMedDate not supplied

Changes in esophageal wall layers during motility: measurements with a new miniature ultrasound suction device.

We have developed a miniaturized ultrasound device that attaches to the gastrointestinal mucosa by suction and produces high-resolution (+/- 0.1 mm) images of the layers of the intestinal wall. The esophageal wall layers in a single sheep were measured during 20 occlusive contractions observed with simultaneous endoscopy, which revealed thickening of the inner circular muscle layer from 1.2 +/- 0.2 mm to 2.2 +/- 0.4 mm (p < 0.01), and during 20 dilations demonstrating thinning of the full thickness of the esophageal wall from 3.6 +/- 0.3 mm to 2.9 +/- 0.3 mm (p < 0.01). Safety experiments performed in two canine stomachs demonstrated no erosions or ulceration at any level of suction. Our investigations indicate that the M-mode suction ultrasound device can safely assess changes occurring in the layers of the esophageal wall during contractions and dilations and should be evaluated for the study of human intestinal motility.

Animals↗
PubMedDate not supplied

Magnetic detection to position human nasogastric tubes.

Placement of nasogastric tubes is one of the most commonly performed diagnostic and therapeutic medical procedures. Proper placement of the tube in the digestive tract below the diaphragm is crucial for efficacy and safety. This study evaluates a magnet detection system that allows percutaneous non-radiographic localization of the nasogastric tube tip. Each volunteer subject had the magnet detector placed over the abdomen, and was then intubated with a magnet-tagged nasogastric tube. Eighty-eight nasogastric tube placements were performed in 22 volunteers. The detection system located the nasogastric tube tip below the diaphragm in all 88 placements. Location in all attempts was confirmed by fluoroscopy. This method of correctly locating the tip of nasogastric tubes may obviate the need for radiographic imaging in most cases.

Adult↗