Robert Craig - US grants

mandible /maxilla; dentures; dental materials; biomaterial evaluation; tensile strength; physical model; biomaterial development /preparation; bite strength; mathematical model; mechanical pressure; computer graphics /printing;

The Center is designed to conduct research and develop new materials for use in dentistry and the health sciences using a multidisciplinary approach by dental materials scientists, materials engineering scientists, and biological scientists. The research will focus on four main areas: (1) novel elastomers to be used for extra oral maxillofacial prostheses and permanently soft complete denture liners, (2) new rigid polymer-ceramic composites for tooth restorative applications having long term wear resistance and in vitro methods to simulate and evaluate the aging of these composites in the oral environment, (3) advanced ceramics for esthetic crowns and bridges with major increases in toughness and fracture resistance, and (4) valid in vitro and animal tests to predict the short and long term biocompatibility of dental materials used for applications ranging from implants to restorative materials. The research projects of the Center will be directed by five faculty members from the dental biomaterials area, four from the materials science and engineering area, one from experimental oral pathology and four from oral biology. These faculty will be assisted by research staff, postdoctoral researchers and graduate research assistants and thus the Center will serve as a training area for future primary researchers in biomaterials. The Center will be administered by the Director and Co-Director with advice from an Internal Review Board having a broad scientific and industrial perspective. The Center will serve as the focus of biomaterials at the University as well as nationally and internationally as a result of interactions with graduate programs, seminars, conferences, and visiting professor and scholar programs.

A mechanical testing machine is essential in the evaluation of biomaterials. Our present Instron TTM Universal Testing Machine was purchased in 1959 and it has been the backbone of our mechanical testing of biomaterials. This model was last produced in 1974 and we have been advised by the Instron Corporation (see Appendix A) that a number of parts are no longer available (e.g. amplidyne, clutch, vacuum tubes, etc.), and repairs may not be possible. State-of-the-art mechanical testers are servohydraulicly driven and have digital output and are computer controlled, plus have biaxial and uniaxial loading. A mechanical tester of this type is essential in evaluating the mechanical properties of composites, substitutes for dentin, maxillofacial materials, ceramics, chewing studies, and strengths of attachment of cements and implants to bone. The ability of such an instrument to test materials under uniaxial and biaxial loading is essential in the future evaluation and development of many and especially implant materials. The Instron we are proposing to purchase will have adequate loading and displacement ranges with computer controlled servohydraulic biaxial loading and special clamping fixtures for brittle materials (ceramics). We also propose purchasing an x-y recorder and an HP 7090A computer to complete the package (note: Instron does not supply these two items).

Breath H2 measurements following carbohydrate administration have been used to characterize its extent of malabsorption by comparing the H2 production following oral administration to that from a known quantity of lactulose. Using a D-xylose kinetic model that determines extent and rate of its absorption, we are studying whether breath H2 following D- xylose administration accurately reflects the extent of its malabsorption.

Using a kinetic model, we have recently completed studies on D-xylose absorption in patients with renal insufficiency, suspected malabsorption, AIDS enteropathy, and normal controls. We have shown that two rate constants characterize the absorption of D-xylose, the rate constant for absorption, ka, and the rate constant for non-absorptive loss, ko. The latter is elevated in diarrheal diseases in which there is rapid transit, or bacterial overgrowth.

The standard technique for studying gastric emptying is the nuclear medicine gastric empyting study which involves the administration of a food that has been mixed with labeled Tecnetium-sulfur-colloid. Over the past 15 years, we have been involved in studying the kinetics of absoption utilizing a D-xylose model that requires the oral and intravenous administration of D-xylose, followed by frequent blood and urine determinations of D-xylose concentration. In addition to providing information about the absorption and disposition of D-xylose, these studies also give data on the lag phase, or the time preceding absorption, which relates to gastric emptying. Our kinetic model will be utilized for both liquid D-xylose and D-xylose administered with food. The results will be compared to the standard nuclear medicine test of gastric emptying. The data obtained will provide additional data on the D-xylose test, and it might provide a relatively simple test of gastric emptying that does not involve the use of radionulide.

stem cell transplantation; artificial immunosuppression; human therapy evaluation; Crohn's disease; immunotherapy; immune tolerance /unresponsiveness; lymphocyte; cyclophosphamide; patient oriented research; human subject; flow cytometry; clinical research;

? DESCRIPTION (provided by applicant): Voltage-gated sodium ion channels (Navs) are integral to both neuronal and muscular signaling and thus are critical to life. The abnormal expression of Navs can lead to a series of ailments including epilepsy, arrythmia, intractable acute and chronic pain, metastatic cancers, erythermalgia, and congenital insensitivity to pain. Despite their importance to human disease, a detailed understanding of the dynamic functionality of these voltage-sensing transmembrane pores continues to elude the scientific community. In order to develop an understanding of how Navs sense and respond to voltage change, we will use molecular probes to construct a model of the tertiary structure of the Site II binding pocket within the ion conduction pore. While there are nine known binding sites distributed around the nine known isoforms of the mammalian Nav, only Site II is within the ion conduction pore of the protein. Within a series of lipophilic alkaloid natural products known to be selective Site II ligands, veratridine is the most efficacious agonist that is readily available from its natural source. Veratridine agonism of the Nav causes activation at normal resting potential, inhibition of inactivation, and reduction of bot single channel conductance and ion specificity. The behavior is extremely intriguing as Site II is located near the center of the conduction pore, however, veratridine ligation at that site profoundly effects the ion selectivity locus and the ion channel gate, both of which are located near the entrances to the pore many Angstroms away. A thorough explanation of how veratridine binding causes these changes will require an extremely detailed model of the veratridine binding pocket. In order to construct this model, ligand-protein complexes of veratridine and a series of related synthetic and semisynthetic molecular probes with a series of heterologously expressed point-mutated single isoform Navs will be characterized by whole-cell electrophysiology. These studies will be used to determine which functional groups on the natural product are essential for its biological activity as well as identify the residues within the ion pore of the Nav that ar integral for veratridine binding. The detailed understanding derived from these studies concerning how ligand binding at Site II deep within the ion pore of the Nav can have such a profound effect on the dynamic function of these transmembrane proteins could lead to the rational design of isoform-specific pharmaceuticals that would serve as treatment for a multitude of intractable diseases.