Robert Davidson, PhD, DDS - US grants

Sensory processing in the central nervous system involves both ascending and descending pathways. For example, ascending nociceptive impulses which mediate oral-facial pain, are influenced by descending control systems originating mainly in the brain stem. In the visual system, ascending impulses from the retina are influenced by descending control systems originating in the cortex. The proposed research examines both a descending modulatory pathway and an ascending sensory pathway. Phase I. Fibers descending to the superior colliculus arise from a wide expanse of prestriate, temporal and parietal cortex. Electrophysiological and behavioral studies in monkeys indicate that this corticotectal system plays an important modulatory role in visuomotor integration. Individual components of this system descend from each of the known subdivisions of visual cortex. Corticotectal cells of each component may form a unique subpopulation of cells within the visuotopic area from which they originate. Our goal in Phase I is to examine one such component namely, the corticotectal pathway from extrastriate area MT. The visual response properties of individual corticotectal cells in MT will be examined with microelectrode recordings in the anesthetized monkey, and compared to a control population of MT cells which do not project to the colliculus. Phase II. Ascending nociceptive information from the oral cavity is relayed to the thalamus by long projection neurons in the superficial layers and lamina V of the medullary dorsal horn. Our goal in Phase II is to determine whether unmyelinated primary afferents synapse on trigeminothalamic cells of lamina V. Trigeminothalamic neurons, identified by antidromic activation from the contralateral thalamus, will be filled with horseradish peroxidase (HRP), and terminals of unmyelinated primary afferent fibers will be labeled with orthogradely transported HRP injected into the dorsal root ganglion. The morphological features of filled cells will be described and the synaptic interaction between these cells and labeled terminals will be analyzed.

Mechanical load, systemic and local factors, and certain factors associated with periodontal inflammation produce remodeling of the periodontium in vivo, and are capable of stimulating metabolic activity in tissue-cultured fibroblast and osteoblast cells. While little is known regarding the mechanisms that directly link the cellular and tissue responses, evidence now suggests that alterations in transmembrane conductances mediated by membrane-bound ion channels are associated with early metabolic events during cell activation. The long-term goal of this project is to understand how periodontal tissues respond to both physiological and pathophysiological influences. Within the proposed project period, one aspect of this question will be examined, namely the ionic mechanisms underlying the response of tissue-cultured osteoblast and osteotrophic, i.e., periosteal and periodontal ligament (PDL), fibroblast cells to factors linked to metabolic and morphological changes in the periodontium. These studies will apply patch-clamp recording techniques to monitor single-channel currents in the cell-attached and excised-patch configurations in order to identify and characterize distinct classes of ion channels resident in these cells; ensemble channel activity, i.e., population conductances, a measure of the "systems-level" response of the cells, will be examined using the whole-cell configuration. The first aim is to study the single-channel response properties of ion channels that are activated or deactivated by mechanical deformation of the osteoblast and fibroblast membrane. The second aim is to determine whether there are ligand-gated conductances across the membrane of these cells, and whether ligand-gated conductances are modulated by mechanical stimulation. The third aim is to study the whole-cell currents mediated by the activity of both ligand-gated mechanosensitive ion channels in these cells.

The entomological collections at The Carnegie Museum of Natural History (CMNH) are scientific resources of international significance, containing 6.5 million prepared specimens and more than five million unprepared ones. Among New World institutions, CMNH has the third largest collection of Lepidoptera and the most diverse collection of Afrotropical insects, associated with a library of exceptional historical coverage for systematic research. The rate that CMNH specimens are being used by researchers and students has risen dramatically in recent years with specimen loans and scientific visitors at the highest levels in CMNH history. Collection growth is at unprecedented levels, due to fieldwork worldwide, donation of private collections, and survey programs addressing biodiversity issues. Specimen integrity, research use, and growth of the collection are hindered by housing problems. More than half of available wooden storage equipment is in perilous condition; only 22% of existing storage is acceptable by modern standards. Old insect drawers housing the Lepidoptera are frag ile and breaking with age, and are unsuitable for using unit trays. Specimens are packed into drawers at maximum density, preventing curation and hindering use in research. Collections in fluids and on glass slides require modern storage. Backlog preparation is required for specimens of unique value, including 130,00 papered Lepidoptera and fragile specimens in alcoholic bulk samples. This three-year project will resolve these problems by accomplishing the following goals: 1. Renovate new space in the Carnegie Museum for expanding collection storage and associated research areas (CMNH cost-sharing; see Appendix 2, J-49). 2. Transfer and rehouse 41% of the Lepidoptera collection into a compactorized storage system containing quality drawers and unity trays (NSF funding requested for labor and storage equipment; CMNH cost-sharing for labor). 3. Transfer to new drawers and unit trays all non-Lepidoptera currently in unacceptable temporary containers (NSF funding requested for labor and storage equipment). 4. Obtain equipment necessary for transfer, maintenance, and curation of the collection (NSF funding requested for stereomicroscopes, computers, printers, and freezers for non- chemical pest control). 5. Provide special attention to specimens of exceptional scientific value ( NSF funding requested for labor to segregate and conserve type specimens and to prepare specimens of greatest value form backlog storage; CMNH cost-sharing for labor to recondition historically important specimens). 6. Provide preliminary curation of taxa currently represented by large numbers of prepared but unsorted specimens (CMNH cost-sharing for visiting specialists).

Understanding the physiological properties of odontoblasts is an important step towards understanding the cellular mechanisms that account for metabolic and transductive processes in dental pulp. Indirect evidence now suggests that such processes are mediated by alterations in transmembrane conductances via ion channels in the odontoblast membrane. Among the most critical of these ionic pathways are those that govern calcium turnover. Calcium regulation is especially important for odontoblast cells, since both intra- and extracellular calcium levels may fluctuate during dentinogenesis, and these cells may be directly involved in transporting calcium to the mineralizing matrix. In addition to mineralogenesis, odontoblast ion channels may also be involved in somatosensation, mediating changes in hydrostatic pressure and/or changes in the osmotic gradient produced by mechanical or hydrodynamic perturbation. The primary objective of the proposed research is to examine the ionic mechanisms underlying the response of these cells to factors associated with dentinogenesis and somatosensory transduction in dental pulp. In these studies I will use patch-clamp recording techniques to monitor single- channel and whole-cell current in the odontoblast membrane using both in vitro and in situ preparations of intact mammalian odontoblast cells. In preliminary studies I have identified an L-type calcium channel as well as a cation-conducting mechanosensitive ("stretch-activated") channel in these cells. The proposed studies will be directed towards a quantitative analysis of these and other conductances, and will include an examination of the effects of dentinotrophic, neurogenic, and inflammatory factors linked to physiological or pathophysiological responses in dental pulp. In preliminary studies l have also identified neural-like non-odontoblast satellite cells in explant-derived pulp cell cultures. Specifically, cultured pulp cells contained a voltage-gated sodium conductance with kinetic properties similar to those of glial or Schwann cells, neuronal satellite cells found in both the peripheral and central nervous systems. In addition, pulp cells were reactive to antibodies that typically label regenerating cells in the nervous system, as well as developing pulp cells in teeth. Thus, these cultures may represent a model for injury, recovery, and/or maturation of non-odontoblast cells in dental pulp. In the nervous system, it has been suggested that such satellite cells may contribute to sensitization of adjacent primary afferents, by alterations in the density, distribution or kinetic properties of it's sodium current. Thus, a second objective of the proposed research is to determine whether the pulp cell sodium current may have a similar functional role in dental pulp, by monitoring its physiological and kinetic properties, and the distribution and density of the underlying sodium channels during maturation of pulp cell cultures. In these experiments, cultures will be treated with agents known to induce differentiation, e.g., growth factors, dexamethasone, or DMSO, and patch-clamp recordings made in parallel with immunohistochemical studies using a monoclonal antibody to the sodium channel itself.

This project will improve and enhance the lepidopteran collections at the Carnegie Museum of Natural History. The entomological collections are scientific resources of international significance, containing 6.9 million prepared specimens with about 6 million unprepared. Among New World collections, it has the second largest collections of Lepidoptera and the most diverse collection of Afrotropical insects. More than 60% of the historical Lepidoptera collection remains in unaccptable, precarious housing, and is jeopardizing specimen integrity. The two year project will rehouse those portions of the historical Lepidoptera collection by providing acceptable storage for more than half of the specimens, providing conservation of specimens of exceptional scientific calue or concern, and providing sorting and preliminary curation of Lepidoptera families represented by high numbers of prepared but unsorted specimens.

Understanding Vanishing Endemism: Survey of the Invertebrates
and Plants of Threatened Montane Habitats in Hispaniola

This biological survey investigates insects, plants, and other organisms from mountain forests on the Caribbean island of Hispaniola (Dominican Republic, Haiti), including some of the most threatened natural habitats on earth. A high percentage of animal and plant species in these habitats are endemic, found nowhere else. Destruction of montane habitats is occurring at an alarming rate and many species are threatened with extinction, including many which provide information essential for understanding biological aspects of related species elsewhere in the New World, especially circum-Caribbean regions such as the southeastern United States, Mexico, Central America, and northern South America. Plants of Hispaniola are the least known of any island in the Antilles. An estimated 80% of invertebrate species in mountainous regions is uncollected and unknown to the scientific community. Project goals are (1) to further an understanding of biological diversity in threatened Caribbean habitats, (2) to improve infrastructure in Hispaniola for research on biodiversity, (3) to rapidly provide recommendations for conservation of endangered Hispaniolan habitats, and (4) to foster creative research on diverse and ecologically significant groups of Caribbean animals and plants.

The principal project accomplishment will be a comprehensive, multi-seasonal biotic inventory of great urgency starting Sept. 2002, ending Aug. 2005. Regions targeted for intensive sampling encompass all six fault-delimited mountain systems in Hispaniola (two in Haiti, four in DR). Sampling emphasizes insects and plants from terrestrial and freshwater systems, especially megadiverse lineages (Lepidoptera, Coleoptera, Diptera, angiosperms). More than 5,320 plants, 150,000 invertebrate specimens, and DNA samples of both will circulate to 170 cooperating specialists worldwide for identification, research, and publication on diverse Caribbean lineages. The project will (1) collect, prepare, and circulate specimens for research, (2) discover and publish on previously unknown organisms, (3) document spatial and temporal occurrence of species and their associates, (4) communicate biological information over the World Wide Web, and (5) apply survey findings to urgent problems in resource management. The findings from this project have significance for scientific research, including systematics, evolution, ecology, and conservation. This is a multi-institutional and international effort based at Carnegie Museum of Natural History (Pittsburgh) with collaborating co-PI's from Smithsonian Institution and Harvard University, staff from key institutions in DR and Haiti (Jardin Botaico Nacional, Museo Nacional de Historia Natural, State University of Haiti), government agencies (Direccion General de Vida Silvestre y Biodiversidad (DR), Ministere de L'Environnement (Haiti)), and private foundations (Fundacion Moscoso Puello, Grupo Jaragua). The project will provide the most complete biotic documentation of Hispaniolan habitats available anywhere, will be essential to preservation and management of these endangered montane habitats, and will be a model for future multinational, multi-institutional biotic inventories in the Caribbean and beyond.

A grant has been awarded the Carnegie Institute to renovate museum storage space and refurbish cabinets and perform other upgrades to the arthropod collection of the institution. The collection contains more than 15 million specimens of insects and other arthropods of great historical and scientific value. The project will retrofit several hundred existing cabinets with new drawers to hold specimens. Pinned specimens will be transferred to the new housings. Data from a large collection of crustaceans and from a collection of slide specimens of fleas will be entered into a database to make the information more accessible to scientists and educators. Consulting experts will provide expertise in curation of several major insect groups. The project will renovate a historic space, the Holland Room, and make the new facility accessible to the public as a showcase for historical systematic research and how modern work is done. Three students per year will be recruited from the University of Pittsburgh for the project, during which time they will be trained in curation and database techniques.

This project will create InvertNet, an on-line virtual museum comprising >50 million insect and related arthropod specimens housed at 22 Midwestern institutions, focusing on the research theme of effects of land use changes on the biota of the Great Lakes and upper Mississippi River drainage basins. These collections document 160 years of environmental change and are an invaluable and irreplaceable resource but, at present, are largely inaccessible to scientists and the general public. Most previous efforts to capture and disseminate invertebrate collection data have focused on label data alone. InvertNet will use advanced digitization and networking technologies to capture and display 2D and 3D images of specimens and labels, and incorporate them into a searchable database. These new techniques should reduce the cost of digitizing insect specimens substantially.

By allowing users to find and view detailed images of specimens of particular species and their associated data labels, InvertNet will provide universal access to collections previously restricted to researchers. It will include links to the popular BugGuide.net insect identification website and to other biodiversity data portals used by researchers, educators, and the general public. This will facilitate and support many aspects of biological research and education, including species discovery and identification, pest management, ecology and biogeography. InvertNet will serve as a model, applicable to other kinds of biological collections, for the use of efficient, computer-assisted procedures to increase the speed and accuracy of collection data capture. This award is made as part of the National Resource for Digitization of Biological Collections through the Advancing Digitization of Biological Collections program and all data resulting from this award will be available through the national resource.