Biomedical subjects

J E Phelps

Publications and source records attributed to J E Phelps.

7 recordsLinked to original sources

PubMed2001

Electrical impedance of cultured endothelium under fluid flow.

The morphological and functional status of organs, tissues, and cells can be assessed by evaluating their electrical impedance. Fluid shear stress regulates the morphology and function of endothelial cells in vitro. In this study, an electrical biosensor was used to investigate the dynamics of flow-induced alterations in endothelial cell morphology in vitro. Quantitative, real-time changes in the electrical impedance of endothelial monolayers were evaluated using a modified electric cell-substrate impedance sensing (ECIS) system. This ECIS/Flow system allows for a continuous evaluation of the cell monolayer impedance upon exposure to physiological fluid shear stress forces. Bovine aortic endothelial cells grown to confluence on thin film gold electrodes were exposed to fluid shear stress of 10 dynes/cm2 for a single uninterrupted 5 h time period or for two consecutive 30 min time periods separated by a 2 h no-flow interval. At the onset of flow, the monolayer electrical resistance sharply increased reaching 1.2 to 1.3 times the baseline in about 15 min followed by a sustained decrease in resistance to 1.1 and 0.85 times the baseline value after 30 min and 5 h of flow, respectively. The capacitance decreased at the onset of flow, started to recover after 15 min and after slightly overshooting the baseline values, decreased again with a prolonged exposure to flow. Measured changes in capacitance were in the order of 5% of the baseline values. The observed changes in endothelial impedance were reversible upon flow removal with a recovery rate that varied with the duration of the preceding flow exposure. These results demonstrate that the impedance of endothelial monolayers changes dynamically with flow indicating morphological and/or functional changes in the cell layer. This in vitro model system (ECIS/Flow) may be a very useful tool in the quantitative evaluation of flow-induced dynamic changes in cultured cells when used in conjunction with biological or biochemical assays able to determine the nature and mechanisms of the observed changes.

Animals↗

PubMed2000

Spatial variations in endothelial barrier function in disturbed flows in vitro.

Hindered barrier function has been implicated in the initiation and progression of atherosclerosis, a disease of focal nature associated with altered hemodynamics. In this study, endothelial permeability to macromolecules and endothelial electrical resistance were investigated in vitro in monolayers exposed to disturbed flow fields that model spatial variations in fluid shear stress found at arterial bifurcations. After 5 h of flow, areas of high shear stress gradients showed a 5.5-fold increase in transendothelial transport of dextran (molecular weight 70,000) compared with no-flow controls. Areas of undisturbed fully developed flow, within the same monolayer, showed a 2.9-fold increase. Monolayer electrical resistance decreased with exposure to flow. The resistance measured during flow and the rate of change in monolayer resistance after removal of flow were lowest in the vicinity of flow reattachment (highest shear stress gradients). These results demonstrate that endothelial barrier function and permeability to macromolecules are regulated by spatial variations in shear stress forces in vitro.

Animals↗

PubMed1985

Evaluation of Angelchik antireflux prosthesis. Long-term results.

Fifteen patients with intractable reflux or its complications were sequentially studied after the placement of the Angelchik antireflux prosthesis. In all, 16 devices were inserted. Parameters were measured before and 3, 12, 24, and 36 months after prosthesis placement and included symptom scoring, esophageal manometry with Tuttle test, endoscopy, suction biopsy, barium swallow, and gastroesophageal scintigraphy. In addition, a subset of patients underwent stimulation/inhibition of the lower esophageal sphincter (LES) with pentagastrin, metoclopramide, edrophonium, and atropine. At a mean time of 16 months postsurgery, 10 of 16 (63%) patients were reflux-free and there was significant improvement in endoscopic, biopsy, and symptom scoring. Post-insertion, there were statistically significant increments in LES pressure with intravenous boluses of pentagastrin, metoclopramide, and edrophonium, and a significant decrease with atropine. Two patients who developed prosthesis herniation into the chest required removal because of ongoing reflux and dysphagia. An additional patient had prosthesis disruption and migration, which also required removal. Four patients with previously failed antireflux procedures had five prostheses placed. All continued to reflux postoperatively. No patient who was initially reflux-free subsequently developed reflux, despite a tendency for LES pressure to decline with time. Although this procedure proved effective for up to 36 months in patients who had had no previous antireflux procedure, the displacement rate (3/16 = 19%), reoperation rate (3/16 = 19%), and the progressive decline in LES pressure over time should make one cautious about its routine use in the surgical treatment of reflux esophagitis.

Endoscopy↗

PubMed1983

An anti-reflux prosthesis in the treatment of gastroesophageal reflux.

The Angelchik anti-reflux prosthesis, a C-shaped, silicone filled device surgically secured around the distal esophagus, received premarket approval by the Food and Drug Administration's Bureau of Medical Devices in 1979. Despite its use in over 9000 patients, there are few physiologic data documenting its effectiveness. We studied ten patients before and 3 months after prosthesis implantation with barium meal, endoscopy, esophageal biopsy, standard acid reflux testing, esophageal manometry, gastroesophageal scintigraphy, and symptom scoring. After surgery all patients were able to discontinue cimetidine and elevation of the head of the bed. Two patients had documentation of mild reflux, one of whom needed to have the prosthesis removed because of its herniation into the mediastinum. Eight patients had no reflux. There was statistically significant improvement in endoscopic, symptomatic, and biopsy grading as well as increased lower esophageal sphincter pressure after surgery. Prosthesis implantation is a promising surgical treatment of intractable esophageal reflux, but we believe additional and long-term studies are needed before its general use.

Adult↗

PubMed1981

Intraluminal pressures generated during esophageal bougienage.

Although esophageal bougienage is a widely used palliative procedure for both benign and malignant esophageal strictures, little is known about the pressure generated or applied to the esophageal wall during this procedure. Accordingly, water-perfused catheters were radially implanted into Maloney dilators to monitor esophageal wall pressure in 13 patients undergoing bougienage for reflux-induced lower esophageal strictures. Maximal pressure generated in this group ranged from a low of 25 to a high of 830 mmHg and was generally higher in individuals with newly dilated strictures and with use of larger bougies. In a control group of 11 patients, resting esophageal wall pressure during dilation was 5 mmHg, a value similar to that measured in stricture patients. Maximal pressure occurred in the area of the lower esophageal sphincter and was not statistically higher than sphincter pressure measured with standard rapid pull-through technique. These studies help to define esophageal wall response to bougienage and the pressures generated at the time of esophageal dilation.

Adult↗

PubMed1979

Net Photosynthesis and Early Growth Trends of a Dominant White Oak (Quercus alba L.).

Examination of the relationship between photosynthesis and growth of a dominant white oak (Quercus alba L.) tree has shown that most growth processes were either completed or well underway before the establishment of significant positive rates of net photosynthesis. Growth was initiated first in the root system (March 3), followed by stem cambial growth (March 26) and later by flower, leaf, and branch growth (April 10). During the period of rapid leaf and branch growth, root and cambial growth ceased and then resumed as the leaves approached maturity. The rapid rate of leaf maturation, the early appearance of positive rates of net photosynthesis in leaves (15% of final size) and the CO(2)-refixing capability of elongating branch tissue reduced the period of time that this white oak tree was dependent on stored reserves. Lower temperature optima and compensation points in developing leaves and stems indicated that the growth-temperature response was optimized for the lower seasonal temperatures observed during the spring. This temperature adaptation further reduced the time that this tree was dependent on stored reserves.

Journal Article↗

PubMedDate not supplied

Intramural extravasation of barium simulating carcinoma of the rectum.

This report describes two patients found to have barium granuloma of the rectum. The lesions appeared as indurated, ulcerated rectal masses that resembled carcinoma on endoscopic examination. Deep mucosal biopsy results demonstrated no malignancy and barium sulfate crystals in tissue macrophages. Radiographs showed persistent soft-tissue barium in the rectum. Past reports of barium granuloma have described ulcerated or polypoid masses in the rectum and anus. Rectal intramural extravasation of barium occurs as a result of asymmetric enema balloon inflation and impaction of the enema tip against the rectal mucosa.

Aged↗