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Biomedical subjects

H Dalen

Publications and source records attributed to H Dalen.

78 records · Page 5Linked to original sources

Transformation of human kidney epithelial cells to tumorigenicity by nickel(II) and V-HA-RAS oncogene.

Nickel is a toxic metal of environmental concern that has been found to be carcinogenic in man and animals. Primary human kidney (NHKE) cells were immortalized or rescued from senescence after exposure to NiSO4. The cell lines (IHKE) displayed abnormal karyotype and anchorage independent growth was observed. However, none of the IHKE cells produced tumor upon injection into athymic nude mice. Transfer of the v-Ha-ras oncogene into IHKE cells induced conversion of the immortalized cells into cell lines (THKE) that were tumorigenic when transplanted into athymic nude mice. Ha-ras DNA was present in the transformed cell lines and expressed at high level.

Animals↗

Starvation-induced autophagocytosis paradoxically decreases the susceptibility to oxidative stress of the extremely oxidative stress-sensitive NIT insulinoma cells.

Glucose and amino acid starvation of cells in culture generally enhances their sensitivity to oxidative stress. This is explained by compensatory autophagocytosis, which results in increased amounts of lysosomal low-molecular-weight, redox-active iron, due to the degradation of metallo-proteins, with a potential increase in iron-catalyzed, intralysosomal oxidative reactions. Such reactions diminish the stability of lysosomal membranes, with resultant leakage of hydrolytic enzymes into the cytosol and ensuing cellular degeneration, often of apoptotic type. However, starvation of NIT insulinoma cells, which are normally remarkably sensitive to oxidative stress, actually attenuated the sensitivity to such stress. We found that starved NIT cells rapidly synthesized ferritin. Moreover, ferritin was found to be autophagocytosed, and the lysosomes were stabilized, as assayed by the acridine orange relocation test. We hypothesize that compensatory autophagocytosis during starvation increases the cytosolic pool of redox-active iron, as a reflection of enhanced transportation of low-molecular-weight iron from autophagic lysosomes to the cytosol, resulting in ferritin induction. The newly formed ferritin would, in turn, become autophagocytosed and bind redox-active lysosomal iron in a non-redox-active form. We also suggest that the proposed mechanism may be a way for oxidative stress-sensitive cells to compensate partly for their failing capacity to degrade hydrogen peroxide before it leaks into the acidic vacuolar apparatus and induces intralysosomal oxidative stress. The insulin-producing beta cell may belong to this type of cells.

Animals↗

N-Glycans influence the in vitro adhesive and invasive behaviour of three metastatic cell lines.

Alterations in cellular glycosylation may play a key role in metastatic behaviour of tumour cells. We studied three metastatic cell lines, LOX (malignant melanoma), FEMX (malignant melanoma) and MA-11 (mammary carcinoma). These cell lines have a very different metastatic behaviour in vivo, and different glycans have been postulated to be partly responsible for these differences. To further investigate the functional role of carbohydrates, these three cell lines have been treated with tunicamycin, an inhibitor of the biosynthesis of N-glycans and benzyl- alpha-N-acetylgalactosamine (benzyl-alpha-GalNAc; BnGalNAc), an inhibitor of mature O-linked glycans. Various in vitro adhesion and invasion assays were undertaken for functional studies. Tunicamycin significantly inhibited adhesion to laminin, but only slightly affected cell adhesion to collagen IV. The same compound significantly decreased cellular invasiveness through a Matrigel invasion chamber. Moreover, tunicamycin reduced homotypic aggregation of cells. BnGalNAc had generally little effect on cell behaviour in in vitro assay. The effects of the inhibitors were, however, to some extent cell line-specific. We conclude that N-glycans, but probably not mature O-glycans have important in vitro functions in cell adhesion to laminin, cell invasion through Matrigel and cellular aggregation in the studied cell lines. These results support the view that carbohydrates are functionally involved in several steps of the metastatic process.

Acetylgalactosamine↗

L-arginine supplementation improves venous endothelial cell but not smooth muscle cell dysfunction induced by prolonged diet-induced hypercholesterolemia.

Hypercholesterolemia induces venous vasomotor dysfunction. This study examines the endothelial and smooth muscle cell vasoreactivity of external jugular veins from rabbits fed either a normal or a 1% cholesterol diet for 8 weeks with and without L-arginine supplementation (2 g/kg day-1 orally for the last 5 weeks). Isometric tension studies were performed on harvested jugular veins. Concentrations of serum cholesterol were 20-fold higher than controls and serum L-arginine twofold higher than untreated animals. Hypercholesterolemia induced hypersensitivity to norepinephrine (p < .05), bradykinin (p < .05), and histamine (p < .05) with a contractile response to serotonin compared to controls. L-Arginine supplementation decreased bradykinin hypersensitivity but had no effect on the changes in norepinephrine serotonin and histamine responses compared to controls. Hypercholesterolemia interfered with relaxation induced by acetylcholine but with L-arginine, normal acetylcholine-induced, endothelium-dependent relaxation returned (54 +/- 10%, compared to 40 +/- 14% in control veins; p > .05). Non-endothelium-dependent relaxation to sodium nitroprusside of precontracted veins was unaffected by the presence of high cholesterol concentrations. This study suggests that L-arginine therapy may ameliorate hypercholesterolemia-induced functional abnormalities in endothelial cells.

Animals↗

A quantitative study of endothelial cell injury in aorto-coronary vein grafts.

Criteria indicating injury of endothelial cells (craters, protrusion, denudation) in saphenous veins for aorto-coronary bypass grafting have been examined and quantitated by use of light-(LM), scanning electron (SEM) and transmission electron microscopy (TEM). The specimens were fixed either by immersion or under pressure. It was shown that the conventional way of handling saphenous vein grafts prior to implantation results in serious damage of the endothelial lining. The factors responsible are presumed to be hypoxia, manual flushing and distension with isotonic saline for blood removal, control of leakage, and counteracting spasm of the graft. Even samples collected by a "no touch" technique and exposed to a short hypoxic interval sometimes revealed slight injury.

Aged↗

Inflammatory reaction as an occlusive mechanism in aortocoronary bypass grafts?

Morphological changes in aortocoronary vein grafts are described in two cases; one dying 5 hours post operatively and the other reoperated 8 months after aortocoronary bypass surgery for graft occlusion. Occlusive thrombi and fibrin deposition on the intimal surface and a focal inflammatory process in the wall of the vein grafts were found in the former. Thrombotic encrustation and organization similar to the manifestations of the thrombogenic theory of atherosclerosis were demonstrated in the latter.

Adult↗