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S A Swanson

Publications and source records attributed to S A Swanson.

At least 19 recordsLinked to original sources
PubMed2000

Modulation of the phosphatase activity of calcineurin by oxidants and antioxidants in vitro.

Previous research has indicated that oxidants, antioxidants and the intracellular redox state regulate the activities of a variety of protein tyrosine kinases, protein tyrosine phosphatases, phospholipases and transcription factors. In order to explore the redox regulation of the serine/threonine phosphatase calcineurin, we have investigated the effects of a variety of oxidants and antioxidants on calcineurin phosphatase activity in vitro. The oxidants hydrogen peroxide, superoxide and glutathione disulfide inhibited the phosphatase activity of calcineurin in a dose-dependent manner. Incubation of purified calcineurin with the antioxidants ascorbate, ascorbate 2-phosphate, alpha-lipoic acid, N-acetyl-L-cysteine and glutathione increased phosphatase activity relative to untreated controls. In contrast, several other commonly used antioxidants, including butylated hydroxytoluene, butylated hydroxyanisole, TEMPOL (4-hydroxy-2,2,6, 6-tetramethylpiperidine-N-oxyl), Trolox (6-hydroxy-2,5,7, 8-tetramethyl-chroman-2-carboxylic acid) and dihydrolipoic acid decreased the activity of purified calcineurin, possibly through prooxidative mechanisms. Although the antioxidant pyrrolidine dithiocarbamate increased the activity of purified calcineurin, it significantly inhibited the activity of calcineurin present in crude fibroblast lysates. These results support and extend the hypothesis that redox factors modulate the phosphatase activity of calcineurin and suggest that further in vivo studies are warranted.

Animals↗
PubMed2000

Evidence of enhanced iron excretion during systemic phosphorothioate oligodeoxynucleotide treatment.

BACKGROUND: Phosphorothioate oligonucleotides, in general, possess properties that could be utilized in the development of therapeutic heavy metal chelators. METHODS: Iron excretion was measured in 16 patients participating in studies to test the safety of OL(1)p53, a 20-mer phosphorothioate oligonucleotide complementary to p53 mRNA. Patients were given OL(1)p53 at doses of 0.05 to 0.25 mg/kg/h for 10 days by continuous intravenous infusion. Urine was collected during the study and analyzed for iron, copper, cadmium, and zinc. RESULTS: We found that phosphorothioate oligonucleotides have a high affinity for iron as well as several other clinically relevant toxic metals. Analysis of patient urine following administration of OL(1)p53 reveals a 7.5-fold increase in iron excretion at low doses (0.05 mg/kg/h). CONCLUSIONS: Phosphorothioate oligonucleotides may have therapeutic potential as heavy metal chelators. Low doses of phosphorothioate oligonucleotide facilitated the excretion of iron. Renal clearance of iron-phosphorothioate oligonucleotide complexes most likely involves secretion into proximal tubules.

Cadmium↗
PubMed1998

Pyrethroid insecticides as phosphatase inhibitors.

In this study we tested the hypothesis that pyrethroid insecticides inhibit calcineurin directly and that inhibition is unaffected by the immunophilin cofactors necessary for calcineurin inhibition by cyclosporin A and FK506. The type II pyrethroid insecticides cis-cypermethrin (c-Cyp), trans-cypermethrin, deltamethrin (Delt), and fenvalerate A alpha (Fen), as well as the type I pyrethroid insecticides cis- and trans-permethrin and S-bioallethrin, were unable to inhibit the phosphatase activity of purified calcineurin under conditions of maximal activation by Ca2+ and calmodulin. Furthermore, c-Cyp, Delt, and Fen did not affect the Ca2+ dependence of calcineurin at 0.1 microM of calmodulin, indicating that Ca2+ binding to calmodulin was not affected by these agents. c-Cyp, Delt, and Fen also failed to inhibit calcineurin phosphatase activity in rat brain supernatant and cultured IMR-32 cells, although potent inhibition was displayed by both cyclosporin A and FK506 in each of these systems. Neither the Ca2+-dependent nor the okadaic acid-inhibitable phosphatase activity toward a 24-amino acid 32P-phospho-peptide substrate was affected by any of the pyrethroid insecticides, indicating that neither type-1 or type-2A phosphatase nor calcineurin is inhibited by pyrethroids. To determine if these results were dependent upon experimental conditions, experiments were repeated using polyethylene glycol-treated glass tubes in place of the standard polypropylene tubes. Regardless of the type of tube, no inhibition of calcineurin by any of the pyrethroid insecticides was observed. These data indicate that the pyrethroid insecticides are not effective inhibitors of calcineurin or other phosphatases.

Animals↗
PubMed1998

Cyclosporin A has low potency as a calcineurin inhibitor in cells expressing high levels of P-glycoprotein.

Cyclosporin A (CsA) is a widely-used immunosuppressant drug whose therapeutic and toxic actions are mediated through inhibition of calcineurin (CN), a calcium- and calmodulin-dependent phosphatase. Inhibition of CN by CsA requires drug binding to its protein cofactor in the inhibition, cyclophilin. Because cyclophilin is a high affinity target for CsA it is expected that this protein can act as a reservoir for the drug in the cell and may be able to inhibit cellular efflux of CsA. P-glycoprotein (P-gp) is known to increase the rate of CsA efflux from CsA loaded cells but it is not clear if the P-gp drug efflux pump can compete effectively with cyclophilin at therapeutically relevant concentrations of CsA. To test the hypothesis that increased expression of P-gp confers protection against CsA-dependent inhibition of CN phosphatase activity, KB-V cells expressing varying levels of P-gp were analyzed to determine the potency of CsA as a CN inhibitor. When intact cells were treated with CsA, a positive correlation was observed between P-gp expression and resistance to CsA-dependent inhibition of CN: the IC50 is approximately 20-fold higher in the multidrug resistant epidermal carcinoma cell line, KB-V, which expresses P-gp at a high level than in the parental, KB, cell line expressing very low levels of P-gp. The resistance displayed by KB-V cells is abrogated by co-administration of the P-gp inhibitor verapamil, whereas verapamil has no effect on CsA potency in control KB cells. In cell lysates from KB-V cells with different amounts of P-gp CsA exhibits equivalent potency, indicating that the difference in sensitivity to CsA among the cell types requires maintenance of cell integrity. These observations support the view that resistance to CN inhibition by CsA occurs in cells with moderately elevated P-gp activity. Therefore, P-gp activity appears to be an important determinant of CsA cellular specificity for both therapeutic and toxic effects.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

The application of thermoelastic analysis to study stresses in human teeth.

The aims of this investigation were to use a full-field thermoelastic technique to study the stress distribution on human teeth subjected to dynamic loads and derive a value for the thermoelastic constant for human enamel. Surface stresses were observed on extracted intact human molar teeth subjected to a load of 200 N cycled at 20 Hz. Measurements were repeated for the same teeth following mesio-occluso-distal cavity preparation and restoration with amalgam and adhesively bonded composite restorations. A value for the thermoelastic constant for human enamel (Km) of 2.25 X 10(-12)m2/N was calculated from physical coefficients in the literature. Unprepared specimens exhibited a comparable magnitude and distribution of stresses to those seen when teeth were restored with adhesively bonded composite restorations. Higher stresses were observed on prepared teeth and there was little change following restoration with amalgam. It can be concluded that a full-field thermoelastic stress analysis technique can be successfully applied to study teeth subjected to axial dynamic loads in vitro and that the resultant stresses are greater in prepared teeth than those restored with bonded composite materials.

Acid Etching, Dental↗
PubMed1996

Measurement of the microhardness and Young's modulus of human enamel and dentine using an indentation technique.

Conventional quasi-static and dynamic test methods have a number of limitations when used to measure the mechanical properties of enamel and dentine. These are due to the complex structure of the material and the small specimen size. In this investigation, a microindentation technique was used to measure the hardness and Young's modulus of human enamel and dentine and any variations with location. Freshly extracted molar teeth were sectioned, and the cut surfaces were ground and polished progressively to 1 micron. The polished surfaces were indented at different distances from the surface and amelodentinal junction with a Knoop indentor. Measurements of the length of the long indentation diagonal were used to calculate a value for hardness. It has been shown that the a-value for Young's modulus of a material can be calculated by comparing the ratio of the long and short diagonals on an indented specimen with the actual ratio of the indentor as any changes will be due to elastic recovery in the specimen. Values obtained for the Knoop hardness of enamel and dentine were in good agreement with those of other workers. It was also possible to show that there was a decrease in hardness with depth from the surface in enamel. The hardness of dentine increased with distance from the amelodentinal junction. Values for Young's modulus for dentine were in good agreement with those of other workers, and there was an increase in modulus with depth from the amelodentinal junction from 8.7 to 11.2 GNm-2. Values for Young's modulus of enamel were not as easy to calculate because of surface- and subsurface damage.

Confidence Intervals↗
PubMed1993

Osteotoxicity of cadmium and lead in HOS TE 85 and ROS 17/2.8 cells: relation to metallothionein induction and mitochondrial binding.

Epidemiological, experimental and clinical data indicate that cadmium and lead are osteotoxins in man and other species. The relative sensitivities of a clonal human osteosarcoma cell line (HOS TE 85) and a clonal rat osteosarcoma cell line (ROS 17.28) to the cytotoxic effects of cadmium and lead were tested in serum-free media without added growth factors. The rat osteosarcoma cells were more sensitive to cadmium with cytotoxicity and inhibition of proliferation at 0.25 versus 0.75 and 1.0 mumol l-1 cadmium, respectively, for human osteosarcoma cell lines. The lower sensitivity to cadmium of human osteosarcoma cells is attributed, at least partly, to induction of metallothionein synthesis by cadmium and zinc in this cell line; in the rat osteosarcoma cell line, they do not induce metallothionein synthesis. Human osteosarcoma cells were more sensitive than rat osteosarcoma cells to lead with inhibition (IC50) of proliferation at 4 mumol l-1 lead and cytotoxicity at 20 versus 6 and over 20 mumol l-1 lead, respectively, for these variables in rat osteosarcoma cells. Both cell lines attained the highest lead concentration in the 15,000 x g (mitochondrial) fraction. The lead in the mitochondrial, microsomal, nuclear and cytosolic fractions of the human cell line did not decrease during 24 h post-washout. Binding of lead was much less stable in the less sensitive rat cells, with 50-100% loss of mitochondrial, microsomal and nuclear lead during 24 h post-washout.

Animals↗
PubMed1991

Effect of sodium butyrate on metallothionein induction and cadmium cytotoxicity in ROS 17/2.8 cells.

ROS 17/2.8 cells, a cloned rat osteosarcoma cell line, are exceptionally sensitive to the cytotoxic effects of cadmium. This sensitivity is associated with the inability of this metal to induce the synthesis of metallothionein, a transition metal-binding protein, which detoxifies this metal by its sequestration. Sodium butyrate induces the synthesis of metallothionein in these cells in a concentration-dependent manner. Treatment with this agent also significantly increases the resistance of these cells to the cytotoxic effects of cadmium and the protective effect of butyrate is reversed upon its removal from culture medium. Butyrate treatment did not significantly alter the accumulation of cadmium by these cells. Hence, the increased synthesis of metallothionein in butyrate-treated cells is not due to increased cellular uptake of cadmium. Inhibition of DNA synthesis due to butyrate was not a sufficient condition to alter metallothionein synthesis or to protect against Cd-induced cytotoxicity. Equivalent inhibition of DNA synthesis with hydroxyurea failed to increase metallothionein synthesis in cadmium-treated cells. These results indicate that modulation of metallothionein gene expression in this cell line is the critical factor in determining cellular sensitivity to the cytotoxic effects of cadmium.

Animals↗
PubMed1991

Polyethylene wear from retrieved acetabular cups.

Laboratory wear testing of ultra high molecular weight polyethylene from 12 Charnley acetabular cups, removed after periods of up to 17.5 years showed that the large patient-to-patient variations in clinical penetration rate cannot be explained by batch-to-batch variation in the wear resistance of the material. Nor was there any evidence of a time-dependent degradation in wear resistance of the material.

Acetabulum↗
PubMed1990

Effect of 5-azacytidine on metallothionein inducibility and sensitivity to lethality of cadmium in rat osteosarcoma (ROS 17/2.8) cells.

ROS 17/2.8 cells, a cloned rat osteoblastic osteosarcoma cell line, were found to be extremely sensitive to the lethal effects of cadmium and to synthesize little, if any, metallothionein in response to cadmium exposure. Culture of cells for 24 h in the presence of 1 microM 5-azacytidine, a cytidine analog, increased the inducibility of metallothionein by cadmium and significantly reduced (P less than 0.001) cytotoxicity. Anion exchange chromatographic analysis of cadmium binding to low molecular mass cytotoxicity. Anion exchange chromatographic analysis of cadmium binding to low molecular mass cytosolic proteins showed that cells treated with cadmium and 5-azacytidine expressed at least 2 isoforms of metallothionein. One isoform of metallothionein with a low affinity for cadmium was constitutively expressed by these cells. The association of poor inducibility of metallothionein by cadmium with extreme sensitivity of cells to cadmium emphasizes the role of this protein in the cellular response to this toxic metal. The modulation of metallothionein inducibility and sensitivity to cadmium by 5-azacytidine treatment suggest that metallothionein gene structure and regulation are altered in ROS 17/2.8 cells.

Animals↗
PubMed1990

Toxicity of cadmium to rat osteosarcoma cells (ROS 17/2.8): protective effect of 1 alpha,25-dihydroxyvitamin D3.

Inadequate vitamin D intake is an important cofactor in clinical and experimental bone disease induced by chronic cadmium exposure. The interaction was investigated by culture of rat osteoblastic osteosarcoma cells (ROS 17/2.8) in a serum-free medium with equimolar concentrations of cadmium chloride and 1 alpha,25-(OH)2 vitamin D3. After addition of cadmium alone to culture medium, the unstimulated secretion of osteocalcin and cellular alkaline phosphatase activity were inhibited at 10 pM, and of DNA synthesis and proline incorporation into collagen at 500 nM. In the presence of equimolar amounts of cadmium and 1 alpha,25-(OH)2 vitamin D3, all four responses paralleled those of 1 alpha,25-(OH)2 vitamin D3 alone up to the inhibitory concentration of 500 nM cadmium. Neither 10 nM 1 alpha,25-(OH)2 vitamin D3 nor 1 microM cadmium induced synthesis of metallothionein in these cells indicating that the protective effect of D3 was not related to the induction of a metallothionein-like protein in ROS 17/2.8 cells. In the presence or absence of D3, cadmium inhibited osteoblastic function at concentrations below the whole-organ concentration of cadmium in bone as reported in experimental and clinical cadmium-induced osteotoxicity. The extreme sensitivity of ROS 17/2.8 cells to cadmium may relate to the absence of metallothionein synthesis.

Animals↗
PubMed1990

Lead inhibits the basal and stimulated responses of a rat osteoblast-like cell line ROS 17/2.8 to 1 alpha,25-dihydroxyvitamin D3 and IGF-I.

Low-level exposure to lead impairs longitudinal growth in children and in experimental animals. The proposed mechanisms include decreased osteocalcin secretion in response to 1 alpha,25-(OH)2 vitamin D3 and decreased response to insulin-like growth factor-I. The interaction of lead, 1 alpha,25-(OH)2 vitamin D3, and insulin-like growth factor-I was investigated in an osteoblast-like cell line from rat osteosarcoma, ROS 17/2.8. Cells were cultured 24 hr in a serum-free medium with lead, 1 alpha,25-(OH)2 vitamin D3, and insulin-like growth factor-I. 1 alpha,25-(OH)2 vitamin D3 (10 nM) evoked a 4-5 X increase in osteocalcin secretion and a 100% increase in cellular alkaline phosphatase activity but no increase in DNA/cell layer. Insulin-like growth factor-I (92.5 ng/ml) evoked a 100% increase of osteocalcin secretion and a 20% increase in cellular DNA contents but no change in cellular alkaline phosphatase activity. Basal and stimulated cellular osteocalcin secretion, cellular alkaline phosphatase activity, and DNA contents were significantly inhibited by addition of 1-10 microM lead. The data are consistent with a toxic effect of lead on osteoblastic function and the cellular responses to 1 alpha,25-(OH)2 vitamin D3 and insulin-like growth factor-I. This interaction may be relevant to impaired childhood growth at low levels of lead exposure.

Alkaline Phosphatase↗
PubMed1990

DNA content of juvenile granulosa tumors determined by flow cytometry.

Juvenile granulosa tumors (JGT) often exhibit worrisome morphologic features, yet usually behave in a benign fashion. Thirteen JGT were examined by flow cytometric analysis of paraffin material to determine if DNA content and cell kinetics are related to prognosis. The patients ranged in age from stillborn to 16 years. Unilateral salpingoophorectomy was the most common therapy. Eleven patients with follow-up were free of disease. Marked nuclear atypia was evident in three cases, and high mitotic counts were observed in six, but only marked atypia correlated with DNA content. Flow cytometry revealed that 46% of the JGT had abnormal DNA content and increased average growth fraction. The neoplasms with the highest DNA indices were found predominantly in postmenarchal girls. JGT may exhibit abnormal DNA content, nuclear atypia, and numerous mitoses, yet behave benignly. DNA flow cytometric studies of higher stage JGT are warranted.

Adolescent↗
PubMed1990

Proliferation markers Ki-67 and p105 in soft-tissue lesions. Correlation with DNA flow cytometric characteristics.

Frozen tissue immunoreactivity with Ki-67, a monoclonal antibody that recognizes a nuclear antigen in nonresting or proliferating cells, was compared to DNA flow cytometry results (from fresh tissue) in a diverse group of 60 soft-tissue lesions. Both DNA index and Ki-67 score were independently reported to be associated with grade and prognosis in sarcomas, but no direct comparison of these two variables was made. It was attempted to measure proliferative activity in fixed paraffin-embedded tissues immunohistochemically in a subset of lesions using an antibody to another nuclear proliferation antigen, p105. Lesions were given a grade according to lesion category (reactive, 1; benign, 2; low-grade malignant, 3; and high-grade malignant, 4). Ki-67 reactivity correlated relatively well with this grading system (r = 0.59); benign lesions usually exhibited a low Ki-67 score and malignant lesions usually but not always exhibited a high score. For example, some malignant fibrous histiocytomas contained only rare positive cells. Some disparity between Ki-67 score and grade and within histologic types indicates some independence from these features, a fact that may be important when correlation with prognosis is performed. However Ki-67 did not correlate well with flow data such as percentage S phase (r = 0.30), percentage S + G2M phases (r = 0.37), or DNA index (r = 0.39). This probably is due to the fact that Ki-67 also marks cells in the G1 phase, whereas these are excluded in flow data analyses. Anti-p105 highlighted almost all nuclei in all cases tested, including fibromatosis, and did not correlate with Ki-67 score, histologic grade or DNA flow cytometric data. Results with p105 could not be favorably affected by titration experiments. It is reasonable to conclude that the Ki-67 score is a variable related to but independent of histologic grade, histologic type, and DNA flow values. Whether it is prognostically important in human sarcomas, as has been suggested, awaits further clinicopathologic study.

Antigens, Surface↗
PubMed1989

Analysis of lymphoepithelioma and lymphoepithelioma-like carcinomas for Epstein-Barr viral genomes by in situ hybridization.

Lymphoepithelioma of the nasopharynx has a strong association with Epstein-Barr virus (EBV). To test the hypothesis that lymphoepithelioma-like carcinomas occurring at other sites are also associated with EBV virus, we used in situ hybridization to analyze 20 cases of lymphoepithelioma and histologically similar lesions and five basaloid squamous cell carcinomas for evidence of EBV genomes. EBV genomes were demonstrated in six of six lymphoepitheliomas of the nasopharynx but in none of five basaloid squamous cell carcinoma. Only one of 14 lymphoepithelioma-like carcinomas was found to contain EBV genomes. The single positive lymphoepithelioma-like carcinoma occurred in the lung of an Asian patient, suggesting that ethnic or geographic influences may be important in determining whether EBV is associated with these nonnasopharyngeal neoplasms. Despite their histologic similarity, most lymphoepithelioma-like carcinomas probably have a different pathogenesis from nasopharyngeal lymphoepithelioma.

Adult↗
PubMed1988

Ectopic midline spinal ganglion in diastematomyelia: a study of its connections.

The connections of an ectopic midline spinal ganglion associated with an asymptomatic sacral diastematomyelia were studied. The ganglion was intercalated in the ventral root of one hemicord and sent its efferents to the dorsal root of the other hemicord. The afferents joined the anterior root to form a midline intradural spinal nerve in the cauda equina. Islands of ectopic glia were present in both roots and the spinal nerve. Both the midline position of the ganglion and the glial heterotopias can be tentatively explained by the failure of incorporation of the dorsal cell wedge ("Zwischenstrang") into the divided neural tube.

Choristoma↗
PubMed1988

Lymphoepithelioma-like carcinoma of the skin.

Carcinomas histologically resembling nasopharyngeal lymphoepithelioma have been identified in the salivary gland, thymus, tonsil, and uterine cervix. Five patients with similar tumors primary in the skin are described. The patients ranged in age from 50 to 81 yr. Four neoplasms were situated on the head, and one was located on the shoulder. Microscopically, they were concentrated in the mid- and deep dermis and lacked connections with epidermis. The pattern was of multiple nodules, smaller irregular islands, and cords. The uniform tumor cells had moderate amounts of lightly eosinophilic cytoplasm and vesicular nuclei with one or two prominent nucleoli. A lymphoid infiltrate was intimately associated with each neoplasm and obscured the malignant epithelium in one. Neither squamous nor glandular differentiation was present, but all tumors exhibited intracytoplasmic mucin. Immunohistochemistry was positive for cytokeratin (5 of 5; diffuse) and epithelial membrane antigen (4 of 5; 3 diffuse, 1 focal). Focal reactivity was also noted for carcinoembryonic antigen (1 of 5), neuron-specific enolase (1 of 5), and vimentin (1 of 5). S100 protein, leukocyte common antigen, Factor VIII-related antigen, prostate-specific antigen (males), Leu M1, and salivary amylase reactivity were absent. One patient developed local recurrence and metastases after 39 mo and was dead of disease at 57 mo. The remaining four were free of disease after 46, 27, 25, and 6 mo of follow-up. The diagnosis of lymphoepithelioma-like carcinoma of the skin is based on microscopic findings and exclusion of occult malignancy. The tumor can be confused with a lymphoid infiltrate and is differentiated from Merkel cell carcinoma primarily on cytologic grounds. The neoplasm may be of adnexal origin.

Aged↗