Search PubMed⌕ Search

Biomedical subjects

T R Dirksen

Publications and source records attributed to T R Dirksen.

At least 19 recordsLinked to original sources
PubMed1995

Alteration of epithelial cell lipid synthesis by N-nitrosonornicotine.

Changes in the lipid composition of a cell membrane due to the binding of one cell modulator may affect binding of a second modulator, whether that binding is receptor-mediated (specific) or non-receptor-mediated (nonspecific). Such altered binding interactions have been demonstrated in oral epithelial cells, wherein N-nitrosonornicotine (NNN), a nonspecific ligand, enhances phorbol ester binding. To characterize membrane changes that may be responsible for such an effect, the current study examined lipid changes in hamster oral epithelial (HCP) cells associated with NNN binding. HCP cultures at two cell densities, 5 x 10(6) cells/100 mm plate (subconfluent cultures) or 10 x 10(6) cells/100 mm plate (confluent cultures) were incubated in Keratinocyte-Serum-Free Medium and exposed to 10 microM NNN or DMSO (solvent control) for 48 h. Lipids were labeled with 14C-acetate, then extracted, separated by thin layer chromatography, and the 14C-lipids located by autoradiography and counted. Exposure of subconfluent cultures to NNN for 48 h, with 14C-acetate present during the final 24 h, resulted in altered phospholipid and fatty acid labeling. Phospholipid labeling increased slightly in the presence of NNN compared to controls, while fatty acid labeling showed a modest but significant decrease in the presence of NNN. Similar changes occurred in the confluent cultures. Prelabeling of lipids in subconfluent cultures, followed by exposure to NNN in the absence of radiolabel, resulted in significantly (P < 0.05) greater phospholipid labeling in the presence of NNN compared to control cultures. At the same time, fatty acid labeling decreased significantly.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Sterol metabolism and oral epithelial cell growth.

Previous studies have demonstrated that as the density of cultured oral epithelial cells increases, there is a concomitant increase in phospholipids and cholesterol ester synthesis and a decrease in that of cholesterol and sterol precursors. Other studies have suggested that the effects of exogenous cholesterol sulfate may be similar to growth responses and influence metabolic steps related to cell density. To further examine this possibility, in the present study lipid synthesis was monitored in hamster cheek pouch epithelial cells in cultures established at different cells densities and in the presence of varying amounts of exogenous cholesterol sulfate. Cell [14C]acetate incorporation into lipids was measured in cultures established at four densities ranging from very subconfluent to very dense (postconfluent) in two media, Dulbecco's modified Eagle's medium (DMEM) with 5% fetal bovine serum and KSFM, a non-serum containing keratinocyte medium. Results indicated that the relative proportion of radiolabel incorporated into different lipid classes changed with cell density. In DMEM, the percentage of radiolabel incorporated into total phospholipids and fatty acids increased significantly with increasing cell density whereas percent incorporation into cholesterol, sterol precursors, and cholesterol esters significantly decreased. In KSFM cultures, proportionate phospholipids labeling was significantly increased in more dense cultures whereas cholesterol and cholesterol esters labeling was significantly decreased. In subconfluent and confluent cultures exposed to 10 or 25 microM cholesterol sulfate, the relative proportions of phospholipid labeling also increased significantly compared to dimethyl sulfoxide (solvent) controls, whereas sterol precursors, fatty acids, and cholesterol esters labeling was significantly decreased. These results indicate that cholesterol sulfate can affect cellular lipid synthesis in a manner similar to that which occurs with increasing cell density, and strengthen the hypothesis that cholesterol sulfate may regulate lipid metabolic pathways related to growth and differentiation.

Animals↗
PubMed1993

The effect of chlorhexidine irrigation on tensile wound strength.

Chlorhexidine in an alcohol vehicle with flavoring agents has been used as a mouthrinse to reduce plaque accumulation in periodontal surgery patients. The purpose of this study was to evaluate the effects of a chlorhexidine-containing mouthrinse on the early tensile wound strength of healing surgical wounds in the rat. Standardized transdermal incisions were made on each lateral abdominal wall of 40 Sprague-Dawley rats. Wounds were irrigated with 10 ml of 0.12% chlorhexidine or 10 ml of normal saline prior to closure. Animals were sacrificed at 48 hours and 96 hours, and the wound area was excised by a standardized protocol. Wound strength was measured using constant speed tensiometry to determine the tensile strength of the healing incision. Results revealed a significantly reduced tensile wound strength at 48 hours for the chlorhexidine-treated group (127 +/- 18.5 gm) compared to the saline irrigation group (150 +/- 32.3 gm) (P < 0.001). However, by 96 hours a significantly increased tensile wound strength was demonstrated by the chlorhexidine treated group (202.1 +/- 21.7 gm) compared to the saline irrigation group (183.2 +/- 37.3 gm) (P < 0.05). These data suggest that chlorhexidine-containing mouthrinse irrigation of wounds produced a reduced early tensile wound strength, but ultimately resulted in shorter healing time.

Analysis of Variance↗
PubMed1981

The consequences of intravenous clofibrate and its implications in the treatment of fat embolism.

Intravenously administered clofibrate has previously been used in treating experimental fat embolism. In the present study, this procedure was found to produce a syndrome identical to classical experimental fat embolism syndrome. Following the intravenous injection of clofibrate, and the lungs of rats became hemorrhagic and edematous (increased weight) and contained fat globules (clofibrate emboli) when observed microscopically. Dosages of 100 to 0.88305 mul/100 gm body weight produced symptoms ranging from acute death due to massive embolism of lungs to a subclinical fat (clofibrate) embolism syndrome.

Animals↗
PubMed1980

Fine structural study of postcastrational adrenocortical carcinomas in female CE-mice.

Postcastrational adrenocortical carcinomas in the CE/Ki inbred strains of mice and the adrenals of noncastrated CE/Ki mice were studied using light and electron microscopic techniques. Most of the tumors appeared as large nodules of cells separated by septae comprised of collagen and blood sinusoids. The majority of tumor cells (Type 1) showed few or no lipid droplets (sudanophobic), polymorphic hyperchromatic nuclei, lack of SER, abundant RER and free ribosomes, prominent Golgi complexes, and few mitochondria with scant internal membranes. Clusters of Type 1 cells were surrounded by a basal lamina. In contrast, Type 2 cells revealed abundant and dilated tubules of SER, large number of lipid droplets and mitochondria with tubulovesicular cristae. These results suggest that Type 2 cells were probably active in steroid hormone synthesis and secretion while Type 1 cells were highly anaplastic and apparently non-steroid-secreting cells.

Adrenal Cortex↗
PubMed1980

Anticaries and antiplaque potential of free-fatty acids in vitro and in vivo.

The efficacy of several fatty acids as antimicrobial, antiplaque, and anticaries agents, as well as their ability to inhibit hydroxyapatite dissolution were examined. All effectively inhibited bacterial growth. Lauric, linoleic, and oleic acids decreased plaque formation and lauric acid inhibited hydroxyapatite dissolution. When used in the food, lauric acid decreased caries in rats, but not significantly.

Animals↗
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↗