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Biomedical subjects

I Romslo

Publications and source records attributed to I Romslo.

At least 55 records · Page 3Linked to original sources
PubMed1987

Uptake of iron from transferrin by isolated hepatocytes. The effect of cellular energy metabolism on the intracellular distribution of iron and transferrin.

The subcellular distribution of iron and transferrin has been studied in isolated rat hepatocytes during uptake of transferrin iron. Iron and transferrin are both rapidly transferred from an extracellular to an intracellular compartment in a process which is slowed down when the cells are deprived of ATP and completely blocked when the cells are incubated at 4 degrees C. The transfer of iron occurs at a higher rate than transferrin. The major part of iron is rapidly incorporated into cytosolic ferritin, i.e. after a 15-min incubation at 37 degrees C 60-70% of cell-associated iron is found in the cytosol as ferritin. The rest of the iron is found in mitochondria (5-10%) and, together with transferrin, in light and heavy endosomes. Following incubation at 4 degrees C, both iron and transferrin are confined to the plasma membrane whereas in ATP-depleted cells the majority of iron and transferrin are recovered in heavy endosomes. The results are consistent with receptor-mediated endocytosis as one mechanism for hepatocyte uptake of iron from transferrin but also suggest an alternative route by which transferrin can donate its iron to the cells and rapidly be released to the extracellular environment without undergoing a complete transferrin cycle.

Adenosine Triphosphate↗
PubMed1986

Amylase, pancreatic isoamylase and lipase in serum before and after endoscopic pancreatography.

Serum amylase, isoamylase and lipase were determined in 17 patients with pancreatic or biliary diseases before and after endoscopic retrograde pancreatography (ERP). Within 1/2-2 hours after cannulation of the pancreatic duct, serum lipase was increased to approximately 4 times the upper reference level and normalized almost completely at 24 hours. A much smaller increase was found in amylase and isoamylase. The elevation in enzyme activities was less in patients with abnormal than with normal ERP. The results suggest that lipase is a more sensitive indicator of pancreatic injury than amylase and isoamylase.

Amylases↗
PubMed1986

Wilson's disease in two siblings--one with fatal outcome.

The clinical and biochemical findings in two siblings with Wilson's disease are described. One of them, an 11-year-old girl, developed acute liver failure terminating in death within a few weeks. Prior to her terminal illness she had been in good health without symptoms suggestive of Wilson's disease. Copper contents of urine, liver, kidney and brain were 20-100 times above the upper normal limits. The liver showed extensive micronodular cirrhosis with nonbile pigment deposits. Her 15-year-old brother had abnormal liver function tests with urinary copper excretion 20 times above the upper normal limit. Treatment with penicillamine was started. Following a short period of deterioration his condition has steadily improved.

Adolescent↗
PubMed1986

Uptake of iron from transferrin by isolated hepatocytes. Relationship to cellular energy metabolism.

The mechanism by which utilization of transferrin-bound iron is linked with cellular metabolism has been studied in isolated rat hepatocytes. The initial binding of transferrin to the hepatocyte is not dependent on metabolic energy, but the subsequent progressive binding of transferrin and uptake of iron depend on metabolic energy and the drainage of reducing equivalents from the respiratory chain. When respiration is completely blocked with cyanide a limiting energy level for the uptake of iron is found at an intracellular concentration of ATP of approximately 0.2 mmol/l. The iron uptake process utilizes ATP hydrolysis, substrate oxidation and dissipation of ionic gradients as energy sources interchangeably.

Adenosine Triphosphate↗
PubMed1985

Iron uptake and heme synthesis by isolated rat liver mitochondria. Diferric transferrin as iron donor and the effect of pyrophosphate.

Isolated rat liver mitochondria accumulate iron from fully saturated transferrin at neutral pH. With 5 microM iron as diferric transferrin, accumulation at 30 degrees C amounts to approx. 40 pmol/mg protein per h. With access to a suitable porphyrin substrate, 70-80% of the amount of iron accumulated is recovered in heme. Mobilization of iron and synthesis of heme both depend on a functioning respiratory chain. Vacant iron-binding sites on mono- and apotransferrin compete with the mitochondria for iron mobilized from transferrin. Pyrophosphate at concentrations in the range 10-50 microM enhances mobilization of iron, counterbalances the inhibitory effect of mono- and apotransferrin and enhances metallochelatase activity. The results emphasize the putative suitability of pyrophosphate as an intracellular iron-transport ligand in situ.

Animals↗
PubMed1985

Use of transcutaneous nerve stimulation in the attacks of acute intermittent porphyria.

A 38-year-old female with acute intermittent porphyria (AIP) was having regular recurrent premenstrual severe attacks of abdominal and chest pain due to the disease. Low-frequency transcutaneous nerve stimulation (TNS) premenstrually prevented or markedly reduced the severity of clinical attacks, associated with a reduced urinary porphyrin excretion. The possible mechanisms of the TNS-induced effects are discussed. This experience suggests that TNS may be an effective and simple prophylactic method in the management of the attacks in AIP. The method can be administered easily by the patient himself as home-treatment and is free of side-effects.

Acute Disease↗
PubMed1985

Determination of porphyrins by high performance liquid chromatography: fluorescence detection compared to absorbance detection.

A comparison is made between determination of porphyrin methyl esters by high performance liquid chromatography (HPLC) with absorbance detection and with fluorimetric detection. Detection limits with absorbance detection vary from 0.8 pmol for 2-COOH-porphyrins to 5 pmol for 8-COOH-porphyrins. With fluorometric detection the corresponding figures are 0.04 pmol and 0.4 pmol. Fluorimetric detection also has a better reproducibility, and it is more specific than absorbance detection. The use of HPLC with fluorimetric detection thus permits rapid, highly efficient and specific quantitative detection and identification of porphyrins in complex biological samples.

Chromatography, High Pressure Liquid↗
PubMed1985

Ferrochelatase deficiency in the bone marrow in a syndrome of congenital hypochromic microcytic anemia, hyperferremia, and iron overload of the liver.

Two sisters had congenital hypochromic microcytic anemia with hyperferremia, heavy iron deposits in the liver, and reduced bone marrow iron. Liver ferrochelatase activity was within normal limits, but in the bone marrow ferrochelatase activity was only 20% of that in healthy controls. There were no findings suggestive of lead intoxication, sideroblastic anemia, or erythropoietic protoporphyria.

Adult↗
PubMed1984

Transferrin as a donor of iron to mitochondria. Effect of pyrophosphate and relationship to mitochondrial metabolism and heme synthesis.

Rat liver mitochondria accumulate iron mobilized from transferrin by pyrophosphate. The uptake has a very low energy dependence, but it is highly dependent on a functioning respiratory chain. Reduction of the ferric-iron-pyrophosphate complex is not linked to any specific respiratory complex. Half of the amount of iron accumulated is passed into heme. Iron once accumulated is very little accessible to chelation by added ferric or ferrous iron chelators. Iron uptake and heme synthesis are maximal if a suitable porphyrin substrate is added simultaneously with iron. The results represent further evidence that pyrophosphate is a possible candidate for intracellular iron transport. Also, the results suggest that iron uptake is coupled to simultaneous porphyrin uptake and heme synthesis.

Animals↗
PubMed1984

Albumin prevents nonspecific transferrin binding and iron uptake by isolated hepatocytes.

Bovine serum albumin inhibits binding of transferrin by hepatocytes in suspension by 60-70%. Iron uptake is inhibited by less than 20%. A Scatchard analysis of the transferrin-binding data reveals a biphasic plot in the absence of bovine serum albumin, but a monophasic plot in the presence of bovine serum albumin. Bovine serum albumin inhibits low-affinity binding of transferrin (125000 molecules/cell), but has no effect on high-affinity binding (38000 molecules/cell). In pronase-treated cells, transferrin binding is reduced by 40%, and when bovine serum albumin is added, the binding is reduced by a further 40%. Corresponding figures for iron uptake are 70 and 10%, respectively. The results are strong evidence that the major part of iron uptake by hepatocytes occurs from transferrin bound to the plasma membrane transferrin receptor.

Animals↗
PubMed1984

Pyrophosphate as a ligand for delivery of iron to isolated rat-liver mitochondria.

Rat liver mitochondria accumulate iron mobilized from transferrin by pyrophosphate. The capacity of the mitochondria to accumulate iron is higher than the capacity of pyrophosphate to mobilize iron from transferrin: with ferric-iron-pyrophosphate as iron donor, iron uptake and heme synthesis are about 10-times that at corresponding concentrations of iron-transferrin plus pyrophosphate. Uptake of iron from ferric-iron-pyrophosphate depends on a functionary respiratory chain and involves reductive cleavage of the ferric-iron-pyrophosphate complex. Apotransferrin inhibits uptake of iron from ferric-iron-pyrophosphate by competing with the mitochondria for iron. The results focus on pyrophosphate as a possible candidate for intracellular iron transport.

Animals↗
PubMed1984

Uptake of iron from transferrin by isolated hepatocytes.

Isolated rat hepatocytes containing 0.56-1.79 micrograms iron/10(6) cells and with an intracellular ATP concentration of 3-4 mM, accumulate iron from transferrin linearly with time for at least 3 h. At 37 degrees C the rate of uptake amounts to 0.3-0.7 pmol/mg cell protein per min. The uptake reaches a saturation level of 21-40 pmol/mg cell protein per h at 2.2 microM iron. At 5 degrees C the uptake does not increase over the time of incubation. Uptake of iron, but not binding of transferrin is increased 4-5-fold at oxygen concentrations 10-20 microM. At oxygen concentrations beyond these limits iron uptake is decreased. Iron taken up at low oxygen concentrations can be chelated by bathophenanthroline and bathophenanthroline disulphonate , but only if the chelators are present during the uptake experiments. The results suggest that iron uptake from transferrin by hepatocytes in suspension involves reductive removal of iron.

Adenosine Triphosphate↗
PubMed1984

Binding of transferrin and uptake of iron by K-562 cells.

Transferrin-mediated uptake of iron has been studied in K-562 human erythroleukaemia cells. K-562 cells accumulate iron from transferrin by a temperature-dependent mechanism linearly with time for at least 150 min. At 37 degrees C the uptake reaches a saturation level of approximately 25 pmol iron/10(6) cells/h at a concentration of iron (as iron-transferrin) of 5 mumol/l. The binding of transferrin reveals saturation kinetics, at 0.2 mumol/l of transferrin specific binding amounts to 1.8 pmol/10(6) cells. Relative to the binding of transferrin the uptake of iron increases with time. The ability of K-562 cells to accumulate iron declines with days in culture by approximately 50% from day 1 to day 5. The results are compatible with iron uptake by receptor-mediated endocytosis of transferrin, dissociation of iron within the cell and exocytosis of apotransferrin.

Cell Line↗