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Biomedical subjects

T R Dirksen

Publications and source records attributed to T R Dirksen.

At least 19 recordsLinked to original sources
PubMed1979

The evaluation of tiodonium chloride as an antiplaque and anticaries agent. II. In vitro antimicrobial activity and in vivo anticaries activity in animals.

The efficacy of tiodonium chloride as an antimicrobial, antiplaque, and anticaries agent was examined. It proved to be an effective antibacterial agent and reduced in vitro plaque formation at concentrations below its bacteriostatic level. It reduced caries in rats when used in the food at 600 microgram/gm but was not effective as a mouthrinse at up to 0.3%.

Animals↗
PubMed1978

Changes in the adrenal cortex of the rat after chronic administration of the steroidogenic inhibitor U-8113.

In concert with studies of the effects of various pharmacologic inhibitors of corticosteroidogenesis on adrenocortical morphology, U-8113, an analog of amphenone B, was administered daily to Sprague-Dawley rats for 7, 14, 21 or 30 day. The primary morphological responses involved increases in adrenal weight, width of zona fasciculata, width of zona reticularis, intracellular lipids, mitochondrial size, mitochondrial vacuolation and crystalline-like inclusions, small coated vesicles, lysosomes, autophagic vacuoles and cholesterol ester clefts. In particular, the increases in lysosomes, coated vesicles and autophagic vacuoles containing morphologically altered mitochondria were considered reflective of mechanisms designed to maintain cellular integrity amidst functional impairment. Lipid analysis revealed marked increases in cholesterol esters and phospholipids, supportive of morphological observations. When permitted a 14 day recovery period following either 14 or 30 days of inhibitor therapy, most fine structural alterations and lipid derangements were diminished, and the cells approximated normal parameters.

Adrenal Cortex↗
PubMed1978

Distribution of 14C-formaldehyde after pulpotomy with formocresol.

Pulpotomies were performed on rhesus monkeys with use of formocresol to determine if there was uptake of 14C-formaldehyde into the systemic circulation after formocresol pulpotomies. Five-minute exposure of pulpal tissue to the 14C-formocresol resulted in the systemic absorption of approximately 1% of the dose. Two hours of exposure of pulp tissue to the 14C-formocresol did not increase the systemic absorption. Multiple sequential pulpotomies resulted in proportionately higher systemic absorption of 14C-formaldehyde. Application of 131I to pulpotomy sites indicated that formocresol compromises the microcirculation of the dental pulp. Autoradiography disclosed extensive concentrations of 14C-formaldehyde in the pulp, dentin, periodontal ligament, and bone.

Absorption↗
PubMed1977

Effect of calcitonin on the phosphorylation of non-histones from cultured bone cells.

32P-uptake into non-histones from bone cell cultures was selectively stimulated in the presence of calcitonin. Comparison of the control and experimental radioactivity profiles of non-histones fractionated by SDS gel electrophoresis showed that, in response to calcitonin stimulation, there was a 2- to 3-fold increase in the specific activity associated with non-histone proteins in the molecular weight range of 10,000 to 45,000 daltons while that of bands between 50,000 to 200,000 decreased.

Amino Acids↗
PubMed1977

Altered enzyme release by virus infected mouse salivary glands.

The rates of release of salivary amylase and esterase from normal and polyoma virus infected mouse submandibular glands were measured in a continuous flow perifusion system. Following stimulation by epinephrine, the rate of release of esterase by the infected glands was significantly greater than that from control glands. The rate of amylase release, while greater from infected glands, was not significantly different. The total enzyme contents from infected and control tissues were similar. Cyclic GMP was found to be higher in the infected glands than the control glands, suggesting one possible mechanism for the higher rates of enzyme release by infected tissues.

Amylases↗
PubMed1976

Peer review of a dental curriculum: how one school did it.

The Curriculum Committee of the Medical College of Georgia implemented a formal course-by-course review of their entire dental curriculum after first adopting positions with respect to faculty philosophical concerns. The strategy adopted was to evaluate the articulation of the various courses into a coherent whole by using reviewers who taught related courses but were outside the particular department or discipline. In general, findings indicated a satisfactory degree of articulation. Some reviewers reported serendipitous outcomes for themselves as a result of reviewing the courses of others.

Curriculum↗
PubMed1975

In vitro lipid synthesis by lathyrogen-treated L-929 fibroblasts.

Aside from cholesterol, cholesterol esters and lyso-lecithin, the de novo lipid synthesic mechanisms which operate in cells grown in the presence of beta-amino-propionitrile are largely depressed and suggest that there may be in operation specific metabolic control mechanisms for regulation of cellular lipid composition.

Acetates↗
PubMed1975

The in vitro effects of Triton WR-1339 on lipid synthesis by bone cells.

Triton WR-1339, administered parenterally, has long been known to be a potent hyperlipemic agent. In vitro lipid biosynthesis is stimulated in liver and brain preparations from animals injected with Triton. Only in a perfused isolated liver system has an in vitro effect of Triton on lipid synthesis been demonstrated. In the present study, lipid biosynthesis has been shown to increase in bone, a third organ system, under the influence of in vitro Triton WR-133. This stimulation affects most major lipid classes. Triton similarly stimulates lipid synthesis in tissue cultures of bone cells. This is the first report of an effect of Triton on lipid synthesis (1) in bone and (2) in any tissue culture system.

Acetates↗
PubMed1975

Effect of beta-aminopropionitrile on in vitro bone lipid synthesis.

The effect of beta-aminopropionitrile (BAPN) on lipid synthesis and 14CO2 production from 14C-acetate by rat calvariae in vitro was investigated by biochemical, histochemical, and autoradiographic techniques. Exposure of bones to 5 mM BAPN throughout a 5-hour incubation period resulted in little effect on lipid synthesis when compared with control bones. Higher BAPN concentrations, up to 100 mM, during this short incubation period resulted in enhanced lipid radioactivity for most of the identified lipid classes. Longer preincubation periods of 20 hours and low BAPN (20 mM) concentrations resulted in enhanced lipogenesis. As BAPN concentrations above 20 mM were employed, lipogenesis decreased to such a level that some lipid classes failed to become labeled with 14C-acetate. 14CO2 production from 14C-acetate by a rat calvariae was affected by BAPN concentration and incubation time in a pattern similar to that of lipid synthesis. Histochemistry demonstrated neutral fat in the osteogenic cells and phospholipids in osteoblasts and the osteoid matrix. Autoradiographic localization of 14C-acetate revealed that the radioactivity was in the osteogenic cells and that this activity was markedly increased after pretreatment of the calvariae with BAPN. This study shows that some concentrations of BAPN enhance lipogenesis by rat calvariae and supports the earlier suggestion that lipids play a role in biologic calcification.

Acetates↗
PubMed1974

In vivo calcification of implanted bone cells.

Bone cells raised in cell culture from the osteogenic cells of newborn rat calvaria were reimplanted in the same species of animals from which the cells were derived. The cells were sealed in Teflon rings containing Millipore filters over both ends. Evidence of calcification occurred inside the implanted ring chambers at 118 and 279 days following implantation in vivo. The calcified matrix produced by the cells had a pattern reminiscent of membranous bone production.

Animals↗