E.A. Ellis

Effects of Chemoreceptor Modification on the Structure of Tsr Arrays

Bacterial chemotaxis is mediated by a sensory complex that is localized to clusters at the cell poles and composed of a mixture of self-associating transmembrane receptors, primarily Tsr (receptors for serine), and the protein signaling proteins CheW and CheA [1]. A large body of evidence suggests that interactions among receptors are key signaling parameters and that arrays function in a highly cooperative manner, mimicking the behavior of allosteric proteins [2, 3]. These receptors function as homodimers, bind ligands in the periplasm, and initiate signaling in the cytoplasm by coupling the autokinase activity of CheA to receptors through CheW. Modulation of kinase activity within arrays is poorly understood, but association of CheA with receptors may be strongly affected by receptor methylation. TEM has been used to investigate the structural characteristics of Tsr by examining their assemblies in native inner membranes of E. coli with or without CheA, CheW, and the attractant ligand serine [4, 5]. Here, we investigate the structural effects of receptor modification on arrays formed by Tsr in fixed states of methylation.

Comparison of Morphology of Sorghum Grain to Resistance to Maize Weevil Sitophilus zeamais

The maize weevil, Sitophilus zeamais Motschulsky, is one of most damaging insect pests of stored grain, including sorghum, Sorghum bicolor (L.) Moench [1]. Maize weevils infest kernels in the field, deposit eggs in stored kernels, and the larva feeds inside and damages the kernel. While the use of sorghum resistant to weevils is an alternative to insecticide, resistance to maize weevils in different sorghum genotypes has not been evaluated for more than 20 years. The first goal of this research was to evaluate the resistance of 20 genotypes of stored sorghum grain to maize weevil. The second goal was to examine the relationship between resistance to weevils and the morphology of the seed coat observed using light microscopy (LM) and scanning electron microscopy (SEM).

Detecting Iron-based Pigments on Ruthenium-coated Archaeological Pottery by SEM-EDS and by Micro-XRF-SEM

1 Microscopy and Imaging Center, Interdisciplinary Life Sciences Building, Mail Stop 2257, Texas A&M University, College Station, TX 77843-2257. 2 American Section, University Museum, University of Pennsylvania, Philadelphia, PA 19104. 3 Microscopy Consulting Technologist, P.O. Box 6124, Thomasville, GA 31758. 4 Department of Agricultural Sciences, West Texas A&M University, Box 60998, Canyon, TX 79016-0001.

Flame Retardant Carbon Nanofiber and Carbon Nanotube Coatings

Due to their ability to reduce volatilization of degradation products during heating, carbon nanofibers (CNFs) and carbon nanotubes (CNTs) are interesting materials for use in nanocoatings to improve flammability resistance [1]. This behavior is commonly attributed to char formation due to nanoparticle aggregation at the surface of the substrate, which forms a protective shield from the fire [2]. Layer-by-Layer (LbL) deposition is an effective processing approach to form nanocoatings, but is difficult to thin section for electron microscopy. In this work, we present a consistent methodology for preparing samples of LbL assembled CNF and CNT-based thin films for transmission electron microscopy (TEM).

Novel Regulated Secretion Mechanism For a Nerve-Secreted Cell Signaling Molecule in C. elegans

Bone morphogenetic proteins (BMPs) are cell-cell signaling molecules that are conserved from sea urchins to vertebrates [1]. The BMP family of ligands is dose-dependent and must undergo complex means of secretion, spatial regulation, and degradation to regulate processes such as extracellular growth and homeostasis. The receptors and signaling pathways that this protein family stimulates is well characterized, but the mechanisms controlling how much of the signal is released are unknown [2]. The free-living nematode C. elegans is an ideal system in which to study this cellular BMP regulatory process, with its conserved molecular pathways, ease of genetic manipulation, and simple, transparent body for visualizing fluorescently tagged transgenic proteins.

BMP Signaling Regulates Extracellular Matrix Composition and Permeability in C.elegans

Bone morphogenetic protein (BMP) pathway signaling plays a critical role in extracellular growth and homeostasis, including basement membrane remodeling and long bone growth. In the small free-living nematode C. elegans, BMP signaling regulates body size development and drug response through an unknown physiological mechanism. Our lab and others have shown animals lacking BMP signaling (bmp(-)) are short and display increased sensitivity to anesthetics, while animals overproducing BMP ((bmp(++)) are long and display resistance to anesthetics [1]. Signaling factors or organization of the cuticle, an extracellular matrix that surrounds and protects the animal from its environment, can influence body shape [2]. Further, large-scale gene expression studies have shown that some cuticular collagen are highly regulated by BMP signaling [3-5]. Based on these data, we tested the hypothesis that BMP affects body length and drug response through organization of the nematode cuticle.

Ship Components, Cargo, or Contamination: Determining the Origin of Wood Fragments Recovered from an Underwater Shipwreck Site

The characteristics of two wood samples (labeled A and B) recovered in August 1991 from an underwater shipwreck site (fig. 1) near the town of Dodos Greece are described using images obtained by scanning electron microscopy (SEM). This underwater site was located in the Bay of Skindos in the Aegean Sea and was dated to 2200 B.C. The wood samples were analyzed to determine if they were associated with the wreck structure, or the wreck cargo, or were modern debris brought into the site by ocean current activity.