Roger Wagner, Ph.D.

Teaching

  • BISC 408 - Mammalian Histology: Microscopic anatomy of human tissues and organ systems at both the light and electron microscopic levels. Two lectures and two 3 hour labs per week.
  • BISC 442* - Vertebrate Morphology: Lectures in this course cover the comparative anatomy of selected vertebrate organisms from functional, developmental and evolutionary perspectives. The laboratory includes dissection and examination of the lamprey, dogfish shark and cat.

Research Interests

X-ray Tomography of Radiolarians and Foraminiferans

Three Dimensional Modeling of Radiolarians with Sub-Micrometer X-ray Tomography

X-ray tomography is used to visualize the surface and interior structure of solid objects on the basis of x-ray attenuation (the proportion of x-rays scattered or absorbed as they pass through an object). A tomographic series is acquired by rotating an x-ray source around a specimen and collecting transmitted x-rays on a series of detectors. The detectors acquire a set of images which are x-ray projections. The are converted to a voxelated 3D files that can be modeled and visualized with AMIRA- a 3d based imaging program.

Radiolarians are amoeboid protists with elaborate radially symmetrical mineral skeletons which are x-ray attenuating. Three dimensional data sets of  radiolarians acquired with high resolution x-ray tomography were computer modeled revealing intricate details of the exterior and interior structure of the skeletons. Digital skeletonization of the same models revealed their essential geometry which was measured with great accuracy based on the voxel size of the original data set.

Three Dimensional Modeling of Vascular Corrosion Casts

Corrosion casting is a procedure in which the blood in blood vessels is replaced by a rapidly-hardening plastic polymer. The surrounding tissue is corroded away with an alkaline solution leaving a plastic cast of all the vessels down to the capillary level perfectly representing the essential geometry of the vascular system. Sharp, high resolution images of corrosion casts can be viewed with a scanning electron microscope (SEM) but the angle of view is restricted and internal cast view is often hidden from view.

Three dimensional data sets of corrosion casts can be acquired from either confocal microscopy (since the casting plastic is fluorescent) or from X-ray tomographic scans (the plastic is also x-ray attenuating). Confocal microscopy affords the greatest resolution but the field of view is very small and limited to small regions. X-Ray tomography permits whole organs such as the kidney to be scanned and computer modeled.

Corrosion casts of the glomerulus of the kidney (blood filtration units) can be imaged with confocal microscopy,  modeled and surface rendered to provide a true representation of the capillary network which filters blood. The filtered materials will eventually end up as urine. Accurate geometrical and mathematical analysis of these models reveals surface area and volume of the blood compartment as well as skeletonization (medial axis transform) which provide a measure of vessel length and connecting regions (nodes).

The vascular systems of whole organs such as the kidney are too large for confocal microscopy and three dimensional data sets must be acquired with high resolution x-ray tomography. These data sets can also be rendered (given a surface) with computer programs such as AMIRA. The models can also be subjected to the same geometric and mathematical analysis as those obtained from confocal microscopy.

Ultrastructure of the Capillary Endothelial Vesicular System

Membraneous vesicular compartments are the most conspicuous features in the cytoplasm of capillary endothelial cells. Their involvement in transendothelial transport (solutes between blood and tissue compartments) has been controversial. This has been due in large part to the lack of three-dimensionality of conventional thin sections for transmission electron microscopy. Whole vesicles and attachment points can be viewed in stereopairs of thick sections with high voltage electron microscopy  but structures are often obscure by overlapping and tilting in only one plan limits viewing organization in three dimensions.

Electron tomography overcomes these limitations by using sections of sufficient thickness to contain a significant fractions of endothelial vesicular structure while resolving the superposition of features by computing a 3D reconstruction of digital slices only a few nanometers thick. Membraneous vesicles free in the cytoplasm and membraneous compartments open to both the luminal and abluminal surface  (transendothelial channels of fused vesicles)  were revealed using this approach. The role of vesicles  as components of the large pore system in continuous capillaries was consistent with these observations.

Selected Publications

Other Information

http://www.apple.com/science/insidetheimage/wagner/

http://www.apple.com/science/insidetheimage/wagner2/
 

Professor Emeritus

Phone: (302) 831-2284

Fax: (302) 831-2281

Email: rags@udel.edu

Office: 005 McKinly Lab

Address:
Department of Biological Sciences
Wolf Hall
University of Delaware
Newark, DE 19716

Education

  • B.S. - Hamline University
  • M.S. - Ohio University
  • Ph.D. - University of Minnesota
  • Postdoctoral - Yale University