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Biomedical subjects

S K Nelson

Publications and source records attributed to S K Nelson.

25 records · Page 2Linked to original sources
PubMed1993

Tat protein of human immunodeficiency virus type 1 represses expression of manganese superoxide dismutase in HeLa cells.

Using a HeLa cell line stably transfected with the tat gene from human immunodeficiency virus type 1, we have found that the expression of the regulatory Tat protein suppresses the expression of cellular Mn-containing superoxide dismutase (Mn-SOD). This enzyme is one of the cell's primary defenses against oxygen-derived free radicals and is vital for maintaining a healthy balance between oxidants and antioxidants. The parental HeLa cells expressed nearly equivalent amounts of Cu,Zn- and Mn-SOD isozymes. Those cells expressing the Tat protein, however, contained 52% less Mn-SOD activity than parental cells, whereas that of the Cu,Zn enzyme was essentially unchanged. The steady-state levels of Mn-SOD-specific RNAs were also lower in the HeLa-tat cell line than in the parental line. No difference was seen in the steady-state levels of Cu,Zn-SOD-specific RNAs. In addition to the decreased Mn-SOD-activity, HeLa-tat cell showed evidence of increased oxidative stress. Carbonyl proteins were markedly higher, and total cellular sulfhydryl content decreased in cell extracts at a faster rate, probably reflecting ongoing lipid peroxidation. HeLa and HeLa-tat extracts were incubated with radiolabeled Mn-SOD transcripts, and the reaction products were subjected to UV crosslinking, digestion with ribonuclease A, and electrophoretic analysis. The results suggest a direct interaction between Tat protein and Mn-SOD gene transcripts.

Blotting, Northern↗
PubMed1992

Copper-marginal and copper-deficient diets decrease aortic prostacyclin production and copper-dependent superoxide dismutase activity, and increase aortic lipid peroxidation in rats.

Agonist challenged aortic prostacyclin production was examined in copper-adequate, -marginal and -deficient rats fed AIN-based diets providing 6.7, 1.7 and 0.8 micrograms Cu/g, respectively. Aortic rings were incubated in Krebs-Henseleit salts, 10 mmol/L HEPES buffer, pH 7.4, 95%:5% O2:CO2, 37 degrees C, and equilibrated for 1 h. Equilibrated rings were challenged with buffer (basal), 273.0 nmol/L thrombin and angiotensin II at 84.6 pmol/L and 846.0 pmol/L. Prostacyclin production, determined at 10 minutes by RIA as 6-keto prostaglandin F1 alpha, in basal and 84.6 pmol/L angiotensin II ring incubations was significantly reduced by 28 to 48% in copper-deficient rats. With thrombin or 846.0 pmol/L angiotensin II prostacyclin production was significantly reduced by 18 to 55% in copper-marginal and copper-deficient rats. Copper-dependent superoxide dismutase activity was significantly depressed by 30 and 57% in aortae of copper-marginal and copper-deficient rats. Lipid peroxidation, estimated by the thiobarbituric acid test, was significantly increased by 85% in copper-deficient rats, with a nonsignificant 40% increase in aortae from copper-marginal rats. The results suggest that the decreases in aortic prostacyclin production in aortae from both copper-deficient and copper-marginal rats are associated, in a dose-dependent manner, with copper-dependent superoxide dismutase depression and increases in aortic lipid peroxidation.

Analysis of Variance↗
PubMed1990

Acquired trigemino-abducens synkinesis.

A 26-year-old woman sustained closed head trauma following a motor vehicle accident. Her injuries included complete trigeminal and abducens nerve palsies. Eleven months later eye muscle surgery succeeded in making her orthophoric in primary gaze although her right abduction deficit persisted. Eighteen months after injury the patient was able to fully abduct her right eye with jaw thrust to the left. With abduction of the right eye there was associated globe retraction and narrowing of the palpebral fissure. This is the second reported case of trigemino-abducens synkinesis. Mechanisms to explain this phenomenon are discussed.

Abducens Nerve↗
PubMedDate not supplied

Long-term cytotoxicity of dental casting alloys.

PURPOSE: Current in vitro cytotoxicity tests for dental casting alloys may be inadequate because they use a short-term test (generally < 168 h) for a material that is present in the mouth for years. A modified in vitro test was used to test the cytotoxicity of 8 dental casting alloys and 3 pure metals. This modified test attempted to simulate the long-term effects of dental casting alloys in the mouth. MATERIALS AND METHODS: Alloys were tested in cell culture either immediately after polishing (initial) or after 10 months of conditioning in a biologic medium containing serum proteins. The cytotoxicities of the 2 conditions were then compared. Alloys were repolished to assess the reversibility of the 10-month conditioning. RESULTS: Alloys with little initial cytotoxicity showed no 10-month cytotoxicity. Alloys with significant initial toxicity showed significantly less toxicity at 10 months. No alloy increased in toxicity after conditioning. Repolishing multiple times did not necessarily reestablish the initial cytotoxicity response. CONCLUSION: The results indicate that short-term cytotoxicity tests may not accurately measure the long-term cytotoxicity of these types of alloys.

3T3 Cells↗
PubMedDate not supplied

Effect of glutaraldehyde-based cold sterilization solutions on light transmission of single-use, plastic light-curing tips.

Previous research has demonstrated that autoclaving of conventional curing tips results in the build-up of an opaque scale on the curing tips ends, greatly reducing light intensity output. Cold sterilization of conventional light-curing tips in most glutaraldehyde-based solutions did not damage the tip or decrease light-transmission quality. However, the specific brand of cold sterilant was found to be of importance, as one specific product was shown to decrease light-tip intensity values irreversibly, even after subsequent tip polishing. A decrease in light intensity output from the curing source significantly affects polymer cure and the biological properties of the restorative material.

Analysis of Variance↗