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Biomedical subjects

K K Park

Publications and source records attributed to K K Park.

At least 19 recordsLinked to original sources
PubMed1991

Scanning electron microscopic study of capillary change in bleomycin-induced pulmonary fibrosis.

The architectural changes which occur in the capillaries are difficult to illustrate without a three-dimensional tool, such as scanning electron microscopy. Therefore, a scanning electron microscopic study was occasionally undertaken to show the capillary changes of lung fibrosis. Fibrosis was induced in twenty rats by an intratracheal injection of bleomycin. After 30 days the rats were sacrificed, and light microscopy and scanning electron microscopy were performed. The vascular trees of both lungs were cast with methacrylate. Light microscopically, the pulmonary fibrosis was patchy and inflammatory cell infiltration was rather sparse. Scanning electron microscopically, the intercapillary spaces became wider; and some capillaries revealed large irregular dilatation. The pleural and alveolar capillaries were variably dilated. The pleural capillary diameter was increased (P = 0.06), and the capillary plexus diameter was decreased (P = 0.00). Distance between the capillary branches of the pleural surface was increased (P = 0.06). The appearance of irregularly shaped capillaries, an increase in diameter with variable dilatation of alveolar capillary rings and a decrease in branching between the capillaries, resulting in a loss of surface area are the main scanning electron microscopic findings of the remodeling which occurs pulmonary capillaries in bleomycin-induced pulmonary fibrosis.

Animals↗
PubMed1990

Antitumor promotion and antiinflammation: down-modulation of AP-1 (Fos/Jun) activity by glucocorticoid hormone.

Glucocorticoid hormones counteract inflammation and phorbol ester tumor promotion and drastically decrease the expression of several extracellular proteases, including collagenase I. Glucocorticoid hormone inhibits basal and induced transcription of collagenase by interfering with AP-1, the major enhancer factor of the collagenase promoter. The mechanism of interference is novel in that it does not require protein synthesis, it depends on the hormone receptor but not its binding to DNA, it occurs at hormone doses one order of magnitude below those required for gene activation, and it involves down-modulation of the trans-activating function of preexisting unbound and DNA-bound AP-1. Coprecipitation experiments suggest direct AP-1-hormone receptor interaction, which also possibly explains the reverse experiment: overexpression of Fos or Jun inhibits the expression of hormone-dependent genes.

Animals↗
PubMed1990

Synthesis and properties of vinyl carbamate epoxide, a possible ultimate electrophilic and carcinogenic metabolite of vinyl carbamate and ethyl carbamate.

Vinyl carbamate reacted with dimethyldioxirane in dry acetone to give a high yield of pure crystalline vinyl carbamate epoxide. This epoxide was characterized by its NMR and MS spectra and elementary analysis. It is unstable at room temperature and has a half-life in water solution of approximately 32 minutes. It reacts with adenosine to form 1,N6-ethenoadenosine and more of this etheno nucleoside was found in hydrolysates of hepatic RNA of male mice injected i.p. with the epoxide than with vinyl carbamate. Tests with Salmonella typhimurium TA1535 showed that this epoxide is a strong direct mutagen. It is also more toxic in the mouse than vinyl carbamate. Studies on the carcinogenicity of this epoxide are in progress.

Animals↗
PubMed1990

Effect of sorbitol gum chewing on plaque pH response after ingesting snacks containing predominantly sucrose or starch.

The purpose of this study was to determine the effect of chewing a sorbitol gum (Trident) for 10 minutes on interproximal plaque pH changes following ingestion of selected sucrose- or starch-containing foods. The snacks containing predominantly sucrose (and/or simple sugars) were chocolate bar, cream-filled cupcakes, cream-filled sandwich cookie, cherry pie and raisins. The snacks containing predominantly starch were oat cereal, granola bars, pretzels, potato chips and corn chips. Plaque pH responses were monitored using an indwelling wire-telemetry system in five adult panelists. The test design involved two sets of 5 x 5 Latin square randomization in which each set consisted of two series of tests. In the first series of tests, the fasted, resting plaque pH was recorded for 5 minutes, panelists ingested the designated snacks for 2 minutes, and the pH response was monitored for the remainder of a 2-hour period. In the second series of tests, the same procedure was followed through the snack ingestion. After the pH response to the snack was monitored for 15 minutes, the panelists were asked to chew one stick of sorbitol gum for 10 minutes and the pH response was then monitored for the balance of the 2-hour period. Results indicated that both the sugar- and starch-containing snacks tested in this study caused significant decreases in interproximal plaque pH. Chewing a sorbitol gum after ingestion of the snacks significantly reduced the demineralizing potential of the plaque. The chewing of sorbitol gum following the ingestion of snacks can be recommended as an adjunct to other caries-preventive oral hygiene measures.

Chewing Gum↗
PubMed1990

The impact of chewing sugarless gum on the acidogenicity of fast-food meals.

The objective of this study was to evaluate the effect of chewing sorbitol gum on plaque pH following the ingestion of acidogenic fast-food meals. Plaque pH response was monitored using an indwelling wire-telemetry system in five adult panelists. From a pilot study with 12 fast-food meals, the most acidogenic breakfast, lunch and dinner were selected for this study. In the first test, the fasted, resting plaque pH was recorded for 5 minutes; panelists ingested the selected meals for 10 minutes, rinsed thoroughly with 50 ml of tap water, and the pH response was monitored for the remainder of a 2-hour period. In the second test series, the same procedures were followed through the post-meal ingestion rinse. After the pH response to the meal was monitored for 5 minutes, the panelists chewed a sorbitol gum for 15 minutes in their usual manner and the panelists were encouraged to move the gum around their mouth, however, it appeared as if they favored the side of their mouth without the partial denture. The pH response was monitored for the balance of the 2-hour period. All panelists ate the test foods, with and without the chewing gum, according to a randomized-block test design. The results indicated that the use of sorbitol gum significantly raised the plaque pH, prevented the subsequent pH drops after the fast-food meal ingestion and reduced the pH curve area under 5.5.

Chewing Gum↗
PubMed1989

Effects of molybdenum on human enamel fluoride uptake and experimental rat dental caries.

The addition of high concentrations of molybdenum to a topically applied sodium fluoride solution did not result in a statistically significant increase in fluoride uptake into subsurface lesions in human enamel when compared to that after treatment with fluoride alone in vitro. The addition of 3000 parts/10(6) molybdenum to a 1000 parts/10(6) fluoride topical solution had no impact in vivo on the cariostatic activity of topically applied fluoride in rats.

Analysis of Variance↗
PubMed1989

Tumor associated proteins of rat skin tumor induced by 7,12-dimethylbenz[a]anthracene.

The incidence of tumor and the time of expression, cellular localization and the molecular weight of tumor associated proteins of rat skin tumor induced by 7,12-dimethylbenz[a]anthracene (DMBA) with or without 12-O-tetradecanoyl-phorbol-13-acetate (TPA) were studied. The time of the development of skin tumors in 0.1% DMBA-TPA treated rats was significantly shorter than that in rats which were treated with DMBA alone. In the complete carcinogenesis case, papillomas developed more slowly and were less common and also squamous cell carcinomas appeared much later. From the analysis of the proteins of each experimental group by SDS-PAGE and two dimensional gel electrophoresis, at least three tumor associated proteins were identified (54kd, pl = 5.66; 27kd, pl = 5.85; 11kd, pl = 4.90). Also these proteins were found in rat dorsal skin from 14 days gestation to 21 days postpartum, and disappeared after 28 days. In conclusions, two stage skin carcinogenesis could be successfully demonstrated in Sprague-Dawley rats and abnormal proteins were produced in DMBA or DMBA-TPA induced skin tumor. The tumor associated proteins of skin tumor induced by DMBA or DMBA-TPA were appeared at the late initiation stage or early promotion stage, and they were localized in plasma membrane and were glycoproteins that are thought to be related to the epidermal differentiation process.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1984

An incisor plaque model in rats.

An in vivo model for studying plaque accumulation in rats has been described. This model investigates plaque formation on the mandibular incisors in animals which have been found to be rapid plaque-formers during a pre-test period. The accessibility of these tooth surfaces permits the removal of plaque prior to initiation of tests, the use of test groups balanced on the basis of plaque-forming potential, and interim assessments of plaque formation throughout the test period. In addition, baseline plaque scores of near zero can be attained, thereby permitting investigations of the impact of experimental measures on plaque formation. Moreover, the model permits intermittent plaque assessments throughout the test period. This model was found to have adequate sensitivity to distinguish effects between antimicrobial agents known to differ in their clinical activity and to detect differences between varying concentrations of the same agent.

Animals↗
PubMed1978

Microsomal metabolism of N-nitrosodi-n-propylamine: formation of products resulting from alpha- and beta-oxidation.

We have identified propionaldehyde, n-propranolo, isopropanol and N-nitroso-2-hydroxy-propylpropylamine following incubation of N-nitrosodi-n-propylamine with a microsomal fraction from rat liver. Based on the yields of the various products, we have shown that beta-oxidation occurs at about 15% of the level of alpha-oxidation, beta- as well as alpha-oxidation was shown to be carried out by the microsomal mixed function oxidase system. N-nitroso-2-hydroxy-propylpropylamine is further oxidized by the microsomal preparation to yield N-nitroso-2-oxopropylpropylamine.

Animals↗
PubMed1977

Mechanism of alkylation by N-nitroso compounds: detection of rearranged alcohol in the microsomal metabolism of N-nitrosodi-n-propylamine and base-catalyzed decomposition of N-n-propyl-N-nitrosourea.

Metabolism of N-nitrosodi-n-propylamine by an isolated rat liver microsomal fraction yielded 17% isopropanol and 83% n-propanol (expressed as a percentage of total propanol formed). Base-catalyzed decomposition of N-n-propyl-N-nitrosourea yielded 39% isopropanol and 61% n-propanol. The values provide evidence for involvement of carbocations in both of these reactions.

Alcohols↗