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Biomedical subjects

I Romslo

Publications and source records attributed to I Romslo.

At least 109 records · Page 6Linked to original sources
PubMed1978

Studies on the utilization of ferritin iron in the ferrochelatase reaction of isolated rat liver mitochondria.

The utilization of ferritin as a source of iron for the ferrochelatase reaction has been studied in isolated rat liver mitochondria. 1. It was found that isolated rat liver mitochondria utilized ferritin as a source of iron for the ferrochelatase reaction in the presence of succinate plus FMN (or FAD). 2. Under optimal experimental conditions, i.e., approx. 50 micromol/1 FMN, 37 degrees C, pH 7.4 and 0.5 mmol/l Fe(III) (as ferritin iron), the release process, as shown by the formation of deuteroheme, amounted to approx. 0.5 nmol iron/min per mg protein. 3. The release process could not be elicited by ultrasonically treated mitochondria, lysosomes, microsomes or cytosol, i.e., the release of iron from ferritin was due to mitochondria and was a function of the in situ orientation of the mitochondrial inner membrane. 4. The release of iron from ferritin by the mitochrondria might be of relevance not only for the in situ synthesis of heme in the hepatocyte, but also with respect to the mechanism(s) by means of which iron is mobilized for transport to the erythroid tissue.

Animals↗
PubMed1978

The diagnosis of iron deficiency by erythrocyte protoporphyrin and serum ferritin analyses.

Free erythrocyte protoporphyrin (FEP) and serum ferritin have been determined in 57 healthy children and in 25 children with varying degrees of iron deficiency. FEP was found to be inversely correlated to the concentration of hemoglobin (r = -0.80) as well as to serum ferritin (r=-0.64). Elevated FEP was found in children with hemoglobin less than 12.5 g/dl, or serum ferritin less than 8 microgram/l. In a group of apparently hematologically normal children between the age of 10--14 years (hemoglobin greater than 12.5 g/dl), a 2-month-trial of iron medication resulted in an increase in hemoglobin and ferritin, and a decrease in FEP, indicating suboptimal supply of iron for hemoglobin synthesis before iron medication. In a patient with iron deficiency (FEP 15.3 mumole/l, hemoglobin 5.2 g/dl), iron therapy was followed by a rapid fall in FEP before any changes in hemoglobin, serum iron transferrin saturation and ferritin could be detected. The rapid fall in FEP during start of treatment in iron deficiency makes FEP a sensitive biochemical parameter on iron homeostasis in iron deficiency anemia.

Adolescent↗
PubMed1978

Porphyrin production and liver involvement in a patient with erythropoietic protoporphyria.

The clinical and biochemical findings in a patient with erythropoietic protoporphyria are described. The patient had an extreme accumulation of protoporphyria in his erythrocytes and there was a thirty-fold increase in stool protoporphyrin. The patient also had elevated protoporphyrin in serum, bone marrow and liver. The porphyrins of the red blood cells, bone marrow and serum had fluorescence spectra different from that of the liver. Urine showed increased copra-, hepta- and uroporphyrins. Ferrochelatase activity in the bone marrow was less than 20% of that of non-porphyric controls. In spite of the extremely high levels of red cell protoporphyrin, the patient was clinically healthy with modest changes in liver function tests and liver histology. The results are discussed in relation to the development of liver damage and the recent findings of the effect of porphyrins on cell metabolism.

Adult↗
PubMed1977

A rapid assay for urinary porphyrins by dual-wavelength spectrophotometry.

A procedure has been developed for the separation and quantitative assay of urinary porphyrins. Urine was directly diluted to a final concentration of 1 MHCl and the amount of porphyrins was determined from the peak-to-trough height deflection of the first derivatives of the absorption spectrum in the region of the Soret band. The ratio uro-/coproporphyrin was determined from the wavelength at which the spectrum intercepted the baseline. The specificity (as shown by a correlation coefficient of 0.99 compared to the method of Doss and Schmidt (1971) Z. Klin. Chem. Klin. Biochem. 9, 415-418), precision (coefficient of variation 5.2 percent) and sensitivity (lower detection limit approx. 0.01 mumol/l) of the present method were highly sufficient to estimate total and different porphyrins in the routine laboratory.

Coproporphyrins↗
PubMed1977

Interaction of conjugated bile acids and detergents with a radiosorbent assay of vitamin B-12.

The effect of conjugated bile acids and detergents on the radiosorbent technique for the determination of vitamin B-12 activity is reported. It is shown that whereas the non-ionic detergent Triton X-100 has no effect on the vitamin B-12-radiosorbent assay, the addition of ionic detergents (e.g. glycocholic acid, taurocholic acid or sodium laurly sulfate) results in a falsely elevated vitamin B-12 activity presumably due to the disruption of the binding of vitamin B-12 to the intrinsic factor-Sephadex complex. This effect may be of importance not only to the radiosorbent assaying of vitamin B-12, but to the in vivo intestinal absorption of vitamin B-12 as well.

Bile Acids and Salts↗
PubMed1977

Enhancement of Tb3+ fluoresence induced by serum proteins other than apotransferrin.

When Tb3+ ions are incubated with human serum, there is a large enhancement in the fluorescence of the Tb3+ ions as revealed by the excitation and emission wavelength pair 288 and 545 nm. The fluorescence enhancement represents the binding of Tb3+ ions not only to (apo)transferrin, but to albumin and gamma-globulins as well. Spectrophotometric evidence indicate involvement of tyrosyl residues at the cation binding site(s). The ion fluorescence induced by albumin and gamma-globulins invalidates the usefulness of the fluorometric determination of transferrin in the routine laboratory.

Apoproteins↗
PubMed1977

Lysozyme determined in serum or urine by a simple nephelometric method.

We describe a nephelometric procedure for determination of lysozyme. A quantitative result is obtained in 2 to 3 min with 50 microliter of serum or urine. At a lysozyme concentration of 12.0 mg/liter, between-day precision was 3.4% and the analytical recovery 96.5-105.5%. The values obtained were a linear function of enzyme concentration below 50 mg/liter, and they agreed with those obtained by absorptiometric determination of the decrease in turbidity of a suspension of Micrococcus lysodeikticus.

Humans↗
PubMed1976

Studies on the ferrochelatase activity of isolated rat liver mitochondria with special reference to the effect of oxidizable substrates and oxygen concentration.

The mitochondrial ferrochelatase activity has been studied in coupled rat liver mitochondria using deuteroporphyrin IX (incorporated into liposomes of lecithin) and Fe(III) or Co(II) as the substrates. 1. It was found that respiring mitochondria catalyze the insertion of Fe(II) and Co(II) into deuteroporphyrin. When Fe(III) was used as the metal donor, the reaction revealed an absolute requirement for a supply of reducing equivalents supported by the respiratory chain. 2. A close correlation was found between the disappearance of porphyrin and the formation of heme which allows an accurate estimate of the extinction coefficient for the porphyrin to heme conversion. The value deltae (mM-1 - cm-1) = 3.5 for the wavelength pair 498 509 nm, is considerably lower than previously reported. 3. The maximal rate of deuteroheme synthesis was found to be approx. 1 nM - min-1 - mg-1 of protein at 37 degrees C, PH 7.4 and optimal substrate concentrations, i.e. 75 muM Fe(III) and 50 muM deuteroporphyrin. 4. Provided the mitochondria are supplemented with an oxidizable substrate, the presence of oxygen has no effect on the rate of deuteroheme synthesis.

Animals↗
PubMed1976

Serum alkaline phosphatase in pregnancy. II. Serial HSAP65degreesC estimations in pregnancy complicated with hypertension and pre-eclampsia.

This is a study of heat-stable alkaline phosphatase (HSAP65degreesC) concentrations in the serum of pregnant women with hypertension (42 cases), mild preeclampsia (40 cases) and severe pre-eclampsia (22 cases). The results are seen in relationship to the occurrence of intrauterine fetal death, growth retardation, intrauterine and neonatal asphyxia as well as the respiratory distress syndrome (RDS) in the newborn. The importance of a precise clinical classification of the patients is stressed. Pathological HSAP values are those which lie either over or under the normal range for HSAP activity. In addition "zig-zag" curves with values within the normal range are characterized as abnormal. Thus, serial estimations give the most reliable results. Serial estimations of HSAP are especially valuable in severe pre-eclampsia. Abnormal HSAP values in the 28th-38th week of pregnancy are a serious prognostic sign. False abnormal HSAP results were found in all 3 patient groups. One possible false normal HSAP curve also occurred.

Alkaline Phosphatase↗
PubMed1976

Transferrin and iron uptake by isolated rat liver mitochondria.

Isolated rat liver mitochondria accumulate iron from the suspending medium when [59Fe]transferrin is used as a model compound. The accumulation proceeds by two different mechanisms, i.e. by an energy-independent and an energy-dependent (uncoupler sensitive) mechanism, which have different time, pH, and temperature dependencies. The energy-dependent accumulation, which is inhibited by ruthenium red and sulphydryl reagents, reaches a saturation level of approx. 30 pmoles iron/mg protein during 30 min incubation. The energy-independent accumulation of iron-transferrin reveals no saturation kinetics, it is inhibited neither by ruthenium red nor by N-ethylmaleimide, and it proceeds linearly for at least 90 min. With [125I]transferrin as a model compound, quantitatively the energy-independent accumulation is as reported for [59Fe]transferrin. There is, however, no energy-dependent accumulation of [125I]transferrin. The results indicate that the energy-dependent accumulation of [59Fe]transferrin represents a process by which mitochondria accumulate iron from transferrin.

Animals↗
PubMed1975

Energy-dependent accumulation of iron by isolated rat liver mitochondria. Requirement of reducing equivalents and evidence for a unidirectional flux of Fe(II) across the inner membrane.

The relationship between the rate of endogenous respiration and the energy-dependent accumulation of iron and calcium was studied in rat liver mitochondria energized by external ATP and inhibited to a variable extent by rotenone. In contrast to the uptake of calcium, that of iron revealed an absolute requirement for reducing equivalents supported by the respiratory chain, which indicates that iron crosses the inner membrane only in the ferrous form. Experimental evidence is presented that a primary event of the energy-linked uptake of iron is that Fe(III) is bound to ligands on the C-side of the inner membrane, ligands which have a unique microenvironment giving the metal a half-reduction potential which is sufficiently high to establish a oxidation-reduction equilibrium with the respiratory chain at the level of cytochrome c. In addition, evidence is presented that this accumulation represents a unidirectional flux of Fe(II) from the C-side to the M-side of the inner membrane and the matrix where it is tightly bound to ligands (proteins?) not yet characterized. As expected, the energy-dependent accumulation of iron is accompanied by an internal alkalinization of the mitochondria analogous to that observed for calcium. A schematic model of the energized accumulation of iron by rat liver mitochondria is presented.

Adenosine Triphosphate↗
PubMed1975

Energy-dependent accumulation of iron by isolated rat liver mitochondria. IV. Relationship to the energy state of the mitochondria.

1. The energy-dependent accumulation of iron by isolated rat liver mitochondria, respiring on endogenous substrates, is strongly dependent on the efficiency of energy coupling in the respiratory chain as measured by respiratory control with ADP and the endogenous energy dissipation. The accumulation reached a saturation level at respiratory control with ADP values (with succinate as the substrate) of approx. 4.0. 2. In the presence of exogenous substrate, the energy-dependent accumulation of iron was markedly reduced, primarily due to binding of iron as carboxylate complexes having less favourable constants than the iron (III)-sucrose complex(es). 3. The effect of added ATP was at least 2-fold, i.e. that of providing energy and that of chelating iron. When the mitochondria respired on endogenous substrate, the energy-dependent accumulation of iron increased at low concentrations of ATP, whereas higher concentrations (greater than 50 mu M) gradually inhibited the uptake. 4. Energization of the mitochondria by the generation of an artificial K-+ gradient across the inner membrane with valinomycin in a K-+-free medium increased the energy-dependent accumulation iron.

Adenosine Triphosphate↗
PubMed1975

Energy-dependent accumulation of iron by isolated rat liver mitochondria. V. Effect of factors controlling respiration and oxidative phosphorylation.

1. Depending on the metabolic state, the addition of iron(III)-sucrose induces an inhibition or a stimulation of the respiration rate when added to isolated rat liver mitochondria. 2. Under conditions identical to those used in the accumulation studies (Romslo, I. and Flatmark T. (1973) Biochim. Biophys. Acta 305, 29-40), the ferric complex induces a decrease in the oxygen uptake concomitant to an oxidation of cytochromes c (+c1) and a(+a3). These results suggest that ferric iron is reduced to ferrous iron by the respiratory chain prior to or simultaneously with its energy-dependent accumulation. 3. On the other hand, the addition of iron(III)-sucrose induces a stimulation of respiration in State 4 and State 3 provided Mg-2+ is present in the suspending medium. In contrast to Ca-2+, iron stimulates State 4 respiration in a cyclic process only within narrow concentration limits; at concentrations of iron above 100 mu M the respiration remains in the activated state until anaerobiosis. The stimulation of State 4 respiration is more pronounced with succinate than with NAD-linked substrates, a difference which partly may be attributed to a stimulation of the succinate dehydrogenase complex. 4. The stimulation of respiration by iron is approx. 3 times higher in State 3 than in State 4 and this difference can be attributed to a stimulation of the adenine mucleotide exchange reaction in State 3 with a concomitant increase in the rate of oxidative phosphorylation, although the P/O ration is slightly diminished.

Adenine Nucleotides↗
PubMed1975

Serum alkaline phosphatase in pregnancy. I. A comparative study of total, L-phenylanine-sensitive and heat-stable alkaline phosphatase at 56 degrees C and 65 degrees C in normal pregnancy.

312 paired, serial estimations of total, L-phenylalanine-sensitive and heat-stable alkaline phosphatase (at two temperatures, 56 degrees C and 65 degrees C) were performed on sera from 31 pregnant healthy women from 18 weeks to term. Heat-stable alkaline phosphatase, determined at 65 degrees C, enriched the serum in a smooth exponential course throughout the second and third trimester, whereas the other enzymic activities investigated showed more irregular increments. There was a slight, but significant correlation between total alkaline phosphatase activity of the placenta and serum heat-stable alkaline phosphatase at term, whereas there was no correlation between the weight of the child at birth and heat-stable alkaline phosphatase in the serum of the mother. It is concluded that to test the feto-maternal unit, determination of serum alkaline phosphatase should be performed at 65 degrees C with due regard to appropriate sampling and experimental design.

Alkaline Phosphatase↗