Medicine and Health Sciences Commons^™

Effects Of Dietary Calcium And Fasting On Osteoclast Recession And Recruitment In Calcium Deficient Rats, Kenneth R. Wright

Loma Linda University Electronic Theses, Dissertations & Projects

The osteoclast, a multinucleated giant cell, has as its role the resorption of bone matrix with consequent release of calcium. The osteoclast is thought to derive from a pluripotent stem cell which also gives rise to monocytes and macrophages. The development, activation, and inhibition of osteoclasts are influenced by a number of systemic and local factors. The release of these factors is influenced by changes in the dietary status of the animal. Calcium deficiency is known to stimulate the recruitment and activity of large numbers of osteoclasts. These osteoclasts can subsequently be inhibited by increasing dietary calcium intake. Disappearance of …

Neurophysiologic Bases For Abnormal Muscle Coactivation Patterns In Hemiparetic Stroke, Julius P.A. Dewald

Loma Linda University Electronic Theses, Dissertations & Projects

To study disturbed muscle activation patterns in hemiparetic stroke, the EMG activity in spastic-paretic and contralateral elbow muscles of 10 stroke subjects were compared during graded directionally varying voluntary isometric contractions. We observed significant shifts in the peak EMG angle and increases in the angular range of EMG activity in the impaired upper limb. Furthermore, we observed stereotypic coactivation of many muscles acting at the same joint or at different joints across all subjects.

The effect of elbow angle changes on muscle coactivation patterns was studied by examining isometric torque-angle relations under passive and active conditions in 8 stroke subjects. …

Development Of Periapical Lesions In Immunosuppressed Rats, Phillip A. Waterman Jr.

Loma Linda University Electronic Theses, Dissertations & Projects

The pathogenesis of periapical lesions is the interaction of the oral flora with the existing host defenses. The role of bacteria has been established in endodontic disease but the contribution of the host defenses in periapical lesion formation is less clear. The purpose of this study was to compare periapical lesion development in immunosuppressed rats with that in normal rats. Thirty-five, eight-week old Sprague-Dawley rats were equally divided into seven groups. Groups 1, 2, and 3 were given weekly injections of Cytoxan, an immunosuppressive agent. Groups 4, 5, and 6 received no immunosuppressive therapy. Group 7 served as a control, …

Transforming Growth Factor-Beta 1 Expression In Developing Ovine Teeth As Visualized By In Situ Hybridization, Søren Jepsen

Loma Linda University Electronic Theses, Dissertations & Projects

Recently we demonstrated that human dentin contained relatively high amounts of transforming growth factor beta (TGF-ß) and proposed that dentin TGF-ß originated from odontoblasts. Because of the suggested role of TGF-ß in mediating cellular interactions in dental cell development by paracrine mechanisms, we studied the expression of TGF-ß message in developing teeth by in situ hybridization. 5 µm serial sections of neonatal sheep mandibular third molars that had been fixed in glutaraldehyde and paraffin-embedded were used for in situ analysis. An [³⁵S]-labeled cRNA probe, complementary to TGF-ß1 mRNA, was constructed from human TGF-ß1 cDNA. Northern analysis of total …

New In Vivo And In Vitro Techniques For Quantification Of Lateral Force Levels That Cause Implants To Fail : A Progress Report On Monkey Research, V. Leroy Leggitt

Loma Linda University Electronic Theses, Dissertations & Projects

Two new techniques for quantification of forces generated by an expansion screw apparatus placed between pairs of cylindrical endosseous titanium implants are described, along with preliminary data gained from their use in Macaca rhesus monkeys. Strain gages were bonded to the expansion apparatus and were calibrated either directly by micro load cell, or indirectly by Instron Machine to reflect the applied force.

Immediate loads of up to 6 kilograms have been applied to the implants with no increase in mobility as verified by a Periotest device. No previous studies on the orthodontic uses of implants have evaluated in vivo forces …

Cortisol In The Ovine Fetus : Its Regulation And Role In Parturition, Ede Marie Apostolakis

Loma Linda University Electronic Theses, Dissertations & Projects

In fetal sheep, circulating cortisol increase during late gestation to abruptly rise 72 hours preceding birth. Although the surge in cortisol is thought to initiate the endocrine cascade which triggers parturition, it is not known what drives the prepartum rise in fetal cortisol. The first study tested the hypothesis that basal cortisol secretion is regulated by adrenocorticotropin (ACTH) which in turn, is controlled by arginine vasopressin (AVP). The fetus challenged with AVP increased plasma ACTH and cortisol concentrations. Pretreatment with an AVP V₁ receptor antagonist blocked AVP-induced plasma ACTH cortisol but failed to alter basal ACTH or cortisol. To …

Modulation Of Rat Hepatic S9-Dependent Mutagenesis, Dna Binding, And Metabolism Of Aflatoxin B1 And Benzo[A]Pyrene By Four Chinese Medicinal Herbs, Brian Yuen Yau Wong

Loma Linda University Electronic Theses, Dissertations & Projects

Extracts of the herbs Oldenlandia diffusa (OD) and Scutellaria barbata (SB) have been used in traditional Chinese medicine for treating liver, lung and rectal tumors while extracts of Astragalus membranaceus (AM) and Ligustrum lucidum (LL) are often used as adjuncts in cancer therapy. In this study, we determined the effects of aqueous extracts of these four herbs on aflatoxin B₁ (AFB₁) benzo[a]pyrene (BaP), benzo[a]pyrene 7,8-dihydrodiol (BaP 7,8-DHD) and benzo[a]pyrene 7,8-dihydrodiol-9,10-epoxide (BPDE)-induced mutagenesis, mediated by enzymes in rat hepatic 9000 x g supernatant (S9), in Salmonella typhimurium TA100. We also studied the effects of these four herbs on …

Plasticity Of The Gnrh Neuronal System During Sexual Maturation Of The Male Djungarian Hamster, Kevin L. Buchanan

Loma Linda University Electronic Theses, Dissertations & Projects

Onset of puberty in male Djungarian hamsters is characterized by increased pituitary gonadotropin secretion and testes maturation, and is controlled by neurons within the brain which secrete gonadotropin-releasing hormone (GnRH). Puberty is associated with increased numbers of morphologically unipolar, but not bipolar, GnRH neurons in the medial preoptic area (MPOA) and diagonal band of Broca (DBB). To test the hypothesis that delayed sexual maturation arrests this increase, males were exposed to short days or administered melatonin. Males with delayed puberty had significantly fewer unipolar GnRH neuron numbers in the MPOA and DBB comparable to pubertal controls in long days. Unipolar …

An Evaluation Of Surface Enamel Damage Following The Debonding Of Ceramic Brackets : A Follow-Up Study, B. Scott Hood

Loma Linda University Electronic Theses, Dissertations & Projects

To evaluate surface enamel damage after debonding ceramic brackets using their manufacturer's recommended methods, sixty four bicuspid teeth were bonded with three different types of ceramic brackets and one type of metal bracket. All the brackets tested utilized mechanical retention only. The brackets were debonded in the mouth seven to ten days after bonding, extracted and evaluated with a scanning electron microscope. The study concluded that: 1) all brackets alter the surface enamel, 2) there is a significant difference in surface enamel damage between the metal bracket and the ceramic brackets utilizing a tensile debonding method, 3) there is no …

The Effect Of Electrical Stimulation Of The Dorsal Raphe Nucleus On Local Cerebral Glucose Metabolism And Epileptogenesis In The Rat, Clifford C. Douglas

Loma Linda University Electronic Theses, Dissertations & Projects

Anatomic connections between the dorsal raphé and the hippocampus have been described in the literature; however, the understanding of the functional importance of these connections is not complete. In these studies the "functional" raphé-hippocampal pathway was elucidated first by the 2-deoxy-d-glucose (2-DG) method, and second by the effect of dorsal raphé electrical stimulation on kindled seizure in the rat. In the 2-DG study, differences in local rates of cerebral glucose metabolism were quantified. The pattern of 2-DG uptake differed significantly from controls (animals with electrodes placed and not receiving an electrical stimulus) and subjects stimulated in the pontine oral reticular …

The Expression And Regulation Of The Hsdk Genes Of Escherichia Coli K-12, Ainu Parkash

Loma Linda University Electronic Theses, Dissertations & Projects

The DNA restriction and modification (R-M) genes in bacteria play a defensive role in the organism, offering protection to the host from invaders such as bacteriophages. The expression of these genes in E. coli K-12 had not previously been studied due to the complexity of the EcoK R-M enzymes. The use of lacZ gene fusion techniques allowed studies of the expression of the hsdK genes for the first time. Operon fusions of Mu(/ac) to the hsdK genes show that the two hsdK promoters, p _res and p _mod, are weak (50 Miller units) and that …