Biomedical subjects

D R Morgan

Publications and source records attributed to D R Morgan.

95 records · Page 6Linked to original sources

PubMedDate not supplied

Gastritis induced by Helicobacter pylori in gnotobiotic piglets.

Helicobacter pylori has recently been recognized as a gastric pathogen in humans. Experimental oral inoculation of gnotobiotic piglets with this organism results in gastritis that exhibits many features of the corresponding disease in humans. In piglets the organism is restricted to the gastric microenvironment and persists in that location despite prompt humoral and cellular responses to antigens of H. pylori. The gnotobiotic piglet model is useful for delineation of the role of suspected bacterial virulence factors (i.e., motility and urease production) in gastric colonization and for preclinical determination of the efficacy of various antimicrobial substances.

Animals↗

PubMedDate not supplied

Characterization of strains of Helicobacter pylori: one-dimensional SDS-PAGE as a molecular epidemiologic tool.

One-dimensional linear sodium dodecyl sulfate-polyacrylamide gel electrophoresis of total proteins, coupled with a computerized numerical analysis, was used to distinguish among strains of Helicobacter pylori. One hundred seventy-five clinical strains and five reference strains of H. pylori from humans, four isolates of Helicobacter mustelae from ferrets, and three isolates of H. pylori-like organisms (HPLOs) from miniature swine were examined. Intraspecies and interspecies comparisons were made through a numerical analysis of protein profiles. It was possible to make valid comparisons for strains run on a single gel. However, variations between gels were significant in some cases, and strains from these gels were not compared. Multiple isolates of H. pylori from one patient clustered at greater than 90% similarity. All strains of H. pylori clustered at greater than 60% similarity, whereas H. pylori was clearly distinguishable (less than 40% similarity) from both H. mustelae and HPLOs. An eventual application of this technique will be to determine whether relapse following therapeutic intervention is due to reinfection (from an exogenous source) or to recrudescence.

Animals↗

PubMedDate not supplied

Gastritis associated with infection by Helicobacter pylori: comparative pathology in humans and swine.

Infection of humans with Helicobacter pylori elicits a multifocal, active, chronic inflammatory response and moderate to severe atrophy of the gastric mucosa. Currently, piglets are the only reported animal model of H. pylori infection. Our objective was to compare the inflammatory response induced in humans with that induced in piglets by H. pylori infection. Samples of gastric mucosa were obtained from H. pylori-infected and uninfected piglets and humans. The composition of the inflammatory cell infiltrate and mucosal atrophy were evaluated by histomorphometric analysis of the biopsied gastric tissue. Infection with H. pylori resulted in a three-fold increase in the volume of inflammatory cells in the gastric mucosa of both humans and piglets. In H. pylori-infected humans, neutrophils composed the bulk of the cellular infiltrate; in piglets, the primary inflammatory cell was the lymphocyte. Both humans and piglets had severe epithelial cell vacuolation and significant reduction of the gastric mucosal surface area. We concluded that pathologic processes induced by infection with H. pylori, which include relatively severe mucosal inflammation, mucosal atrophy, and epithelial vacuolation, are similar in piglets and humans but that the primary inflammatory cell types are distinctly different in the two species.

Adult↗

PubMedDate not supplied

Measured performance characteristics of a solid-state linear detector array.

Experimental studies of a solid-state linear detector array developed for a prototype scanning slit digital chest radiographic unit have been completed. The detector consists of a strip of scintillating material, optically coupled to a linear silicon photodiode array. Measured performance characteristics of the detector, such as sensitivity, modulation transfer function, and detective quantum efficiency, are presented for several different scintillators. Results indicate that direct x-ray absorption events in the silicon photodiode can degrade detective quantum efficiency. Results also indicate that the inexpensive preamplifier circuits used in the digital chest prototype contribute negligible noise at diagnostic x-ray photon fluence rates.

Mathematics↗

PubMedDate not supplied

Performance characteristics of a dual-energy detector for digital scan projection radiography.

An energy discriminating x-ray detector has been developed for dual-energy, scan projection digital radiography. The detector is comprised of a pair of x-ray intensifying screen/linear photodiode arrays, aligned one behind the other. Energy discrimination is achieved by employing a low atomic number phosphor in the front screen and a high atomic number phosphor in the back screen. The x-ray response, modulation transfer function, and defective quantum efficiency of the detector are reported along with the experimental methodology utilized for the measurements. Also presented is an analysis which indicates that in a typical patient's lung field, the detector can resolve the projected density (g/cm2) of a 3-mm-thick, 1-cm2 area of bone to better than 1.5%.

Humans↗