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Biomedical subjects

G Jansen

Publications and source records attributed to G Jansen.

At least 127 records · Page 7Linked to original sources
PubMed1989

Cytotoxicity of methotrexate and trimetrexate and its reversal by folinic acid in human leukemic CCRF-CEM cells with carrier-mediated and receptor-mediated folate uptake.

The cytotoxic effects of the antifolates methotrexate (MTX) and trimetrexate (TMQ) were investigated for two human leukemic CCRF-CEM cell lines, one expressing the "classical" reduced folate/MTX carrier (CEM-RF), another lacking this carrier but expressing a membrane associated folate binding protein (CEM-FBP). CEM-FBP cells were found to be highly resistant to MTX compared to CEM-RF cells, especially in short exposures. For example, after 4 h incubation, IC50 values for MTX were 251 microM and 0.98 microM for CEM-FBP and CEM-RF cells, respectively. On the other hand, CEM-FBP cells were much more sensitive to the lipophilic antifolate TMQ than CEM-RF cells as shown by IC50 values (after 4 h of exposure) of 0.059 microM and 7.5 microM, respectively. Finally, the reversal of TMQ cytotoxicity by folinic acid was significantly impaired for CEM-FBP cells, in contrast to CEM-RF cells. These results indicate that the nature of the membrane transport system for folates can be a critical determinant in tumor cell sensitivity or resistance to antifolates.

Biological Transport↗
PubMed1989

Increased survival of ischaemic musculocutaneous flaps in rats after acupuncture.

The effects of acupuncture on survival of ischaemic musculocutaneous flaps were investigated in the rat. A dorsal cranially based standard flap (2 X 7 cm) was elevated and sutured back in position. The percentage survival of the flaps was estimated after 6 days. Manual acupuncture, electro-acupuncture but not superficial acupuncture significantly increased the survival of the flaps compared to untreated controls. The highest flap survival (92%) was obtained with repeated post-operative high-intensity electro-acupuncture. It is concluded that acupuncture treatment markedly increases experimental flap survival and may be of clinical importance for treatment of local ischaemia.

Acupuncture Therapy↗
PubMed1988

Profiling of plasma cholesterol ester and triglyceride fatty acids as their methyl esters by capillary gas chromatography, preceded by a rapid aminopropyl-silica column chromatographic separation of lipid classes.

A rapid procedure for the isolation of plasma cholesterol ester and triglyceride fractions with aminopropyl-silica columns, followed by analysis of their fatty acid compositions by capillary gas chromatography with flame ionization detection, is described. Within-series and long-term (six months) series-to-series precision were investigated. The isolation procedure caused minimal cross-over between the two lipid classes. Reference values for 57 apparently healthy Dutch adults were established and compared with data reported from other countries. Feeding of rats with four diets differing in their fatty acid compositions showed the relationship between the composition of the fatty acids in the diet and those esterified to cholesterol in plasma. The method is of potential usefulness to the establishment of the compliance of dietary interventions and basic dietary experiments.

Adult↗
PubMed1986

Capillary gas chromatographic profiling of urinary, plasma and erythrocyte sugars and polyols as their trimethylsilyl derivatives, preceded by a simple and rapid prepurification method.

A capillary gas chromatographic method for the profiling of trimethylsilylated mono- and disaccharides and polyols in urine, plasma and unwashed and washed erythrocytes is described. The prepurification method is based on the moderate inhibition of the derivatization experienced in the presence of physiological amounts of inorganic salts and the relative stability of the formed trimethylsilylethers towards treatment with water and dilute hydrochloric acid. Series to series quality control data for 31 sugars/polyols in a pooled urine are given. The method was used to establish age-dependent concentrations of 18 sugars/polyols in urines of 72 control persons on a free diet. Gas chromatographic profiles and quantitative data obtained from urines of pediatric patients with galactosemia treated with a diet low in lactose and galactose, type 1 hereditary tyrosinemia treated with a diet low in phenylalanine and tyrosine, and a neurological disorder with a high calorie gastric drip feeding, are presented and discussed. Examples of the profiling of sugars/polyols in the plasma, unwashed and washed erythrocytes of a healthy adult, and the plasma of a newborn with galactosemia prior to treatment, are given.

Adolescent↗
PubMed1986

Increase of plasma and red cell cholesterol sulfate levels in induced hypothyroidism in man.

Plasma and erythrocyte cholesterol sulfate-, erythrocyte cholesterol-, and serum unesterified- and total cholesterol levels of ten athyreotic thyroid cancer patients were measured during triiodothyronine supplementation, and subsequently at the end of a two weeks withdrawal of this medication. The results showed that in the hypothyroid state all above mentioned parameters increased except for the erythrocyte cholesterol level, which remained unchanged. The interrelationships between these parameters, and the exchange mechanism of cholesterol sulfate between plasma and erythrocytes are discussed.

Adult↗
PubMed1986

Glycolytic activity in human red cell populations separated by a combination of density and counterflow centrifugation. Evidence for an improved separation of red cells according to age.

Human red blood cells were separated by a discontinuous Percoll density gradient into fractions of increasing density. Red cells comprising the lowest and highest density fractions, respectively, were subsequently separated according to mean cell volume (MCV) by means of counterflow centrifugation. The activities of 4 red cell age-dependent enzymes (hexokinase (HK), pyruvate kinase (PK), glucose-6-phosphate dehydrogenase (G6PD) and aspartate aminotransferase (ASAT) were highest in the red cell fraction with low density/large MCV, although the difference from red cell enzyme activities in the total low density fraction was not significant. These 4 enzyme activities were lowest in the fraction of red cells with high density/small MCV. The relative activities of the enzymes in the high density/small MCV fraction, as compared to the unseparated cell population, were: HK (58%), PK (49%), G6PD (53%) and ASAT (28%). These activities were all significantly lower than those measured in the total high density red cell fraction. The rates of lactate production in the low density/large MCV cells (0.89 +/- 0.15 mumol X min-1 X 10(-11) cells) is approximately 3-fold higher than in high density/small MCV cells (0.33 +/- 0.03 mumol X min-1 X 10(-11) cells). This latter value is 1.8-fold lower than the rate of lactate production in the total high density red cell fraction (0.59 +/- 0.14 mumol X min-1 X 10(-11) cells) and is, in contrast to lactate production in other density/size fractions, insensitive to phosphate as a metabolic stimulus. It is argued that the combination of density gradient and counter-flow centrifugation offers a greater potential for obtaining an old red cell population than classical red cell density centrifugation alone.

Cell Separation↗
PubMed1985

Determination of inorganic sulphate in plasma by reversed-phase chromatography using ultraviolet detection and its application to plasma samples of patients receiving different types of haemodialysis.

The determination of sulphate in plasma is described, making use of reversed-phase high-performance liquid chromatography with ultraviolet detection. The concentration of inorganic sulphate determined in plasma of twenty healthy volunteers was 0.307 +/- 0.092 mmol/l (mean +/- S.D.). In one stable chronic dialysis patient the kinetics of plasma sulphate removal were monitored during and after one single pass dialysis. In addition, plasma sulphate concentrations were determined in three stable chronic dialysis patients during a consecutive scheme of two single pass dialyses, five Redy dialyses and three single pass dialyses. As expected, plasma sulphate accumulates in plasma to a high steady-state level under Redy dialysis, whereas during single pass dialysis sulphate is efficiently removed.

Adult↗
PubMed1985

Characteristics of hexokinase, pyruvate kinase, and glucose-6-phosphate dehydrogenase during adult and neonatal reticulocyte maturation.

Erythrocytes from adults and newborn infants (at term and premature) were separated by Percoll density gradient centrifugation into four fractions of increasing density. Glycolytic enzymes, especially the age-dependent ones, hexokinase (EC 2.7.1.1, HK), pyruvate kinase (EC 2.7.1.40, PK), and glucose-6-phosphate dehydrogenase (EC 1.1.1.49, G6PD) were studied during reticulocyte maturation and further red cell senescence. Analysis of the fraction with lowest density showed an almost linear and steep decline of HK, PK, and G6PD activity with a decreasing number of reticulocytes. In the next three fractions of increasing density, the activity decline was far less. These data are therefore illustrative for a biphasic activity decay pattern of HK, PK, and G6PD during both adult and neonatal red cell aging. The strong decline in HK activity could not be ascribed to the disappearance of a particulate (mitochondrial) bound fraction of the enzyme during reticulocyte maturation. All hexokinase activity in human reticulocytes was found to be cytosolic in contrast with rabbit reticulocytes in which 70% of HK activity was particulate.

Adult↗
PubMed1985

Age dependent behaviour of red cell glycolytic enzymes in haematological disorders.

The age dependent behaviour of 11, mainly glycolytic, red blood cell enzymes in 26 patients with various haematological disorders has been investigated after separation of red blood cells by discontinuous density gradient centrifugation. The frequency of enzyme deficiencies in the old cells of these patients was significantly increased in comparison with the unseparated cells, 29 and 13 deficiencies, respectively. Particularly hexokinase activity, although normal or even increased in unseparated cells, was found deficient in old cells in seven cases. In addition, an increased number of phosphofructokinase deficiencies was observed in the patients' old cells (eight cases) as compared to the unseparated cells (three cases). However, the red blood cells of the majority of these patients were found to contain increased enzyme activities, irrespective of cell age. Enzyme activities in the youngest cell population did not correlate with the reticulocyte count. Cases of high pyruvate kinase and hexokinase activities were studied for kinetical, electrophoretical and immunological properties of the respective enzymes, but no abnormalities could be demonstrated, indicating an increased synthesis of these enzymes.

Centrifugation, Density Gradient↗
PubMed1985

Early diagnosis of recessive X-linked ichthyosis: elevation of cholesterol sulfate levels in placental sulfatase deficiency before the onset of skin symptoms.

Children and adults with recessive X-linked ichthyosis have elevated levels of cholesterol sulfate, a substrate of the deficient enzyme microsomal sulfatase, in blood, erythrocyte membrane, and ichthyotic scale. We investigated cholesterol sulfate levels in patients with microsomal sulfatase deficiency before birth in amniotic fluid and in maternal plasma and erythrocytes, in cord blood (plasma and erythrocytes), and in plasma in the first month of life before and after onset of skin symptoms. Levels in amniotic fluid and cord blood were elevated. The plasma levels in the first month, before as well as after onset of skin symptoms, were within the range found in older patients with manifest skin symptoms.

Adult↗
PubMed1984

Inactivation and affinity-labeling of rat liver iodothyronine deiodinase with N-bromoacetyl-3,3',5-triiodothyronine.

The thyroid hormone derivative N-bromoacetyl-3,3',5-triiodothyronine (BrAcT3) acts as an active site-directed inhibitor of rat liver iodothyronine deiodinase. Lineweaver Burk analysis of enzyme kinetic measurements showed that BrAcT3 is a competitive inhibitor of the 5'-deiodination of 3,3',5'-triiodothyronine (rT3) with an apparent Ki value of 0.1 nM. Preincubations of enzyme with BrAcT3 indicated that inhibition by this compound is irreversible. The inactivation rate obeyed saturation kinetics with a limiting inactivation rate constant of 0.35 min-1. Substrates and substrate analogs protected against inactivation by BrAcT3. Covalent incorporation of 125I-labeled BrAcT3 into "substrate-protectable" sites was proportional to the loss of deiodinase activity. The results suggest that BrAcT3 is a very useful affinity label for rat liver iodothyronine deiodinase.

Affinity Labels↗
PubMed1984

Pyruvate kinase and the "high ATP syndrome".

The erythrocytes of a patient with the so-called "high ATP syndrome" were characterized by a high ATP content and low 2,3-diphosphoglycerate level. The pyruvate kinase activity was specifically increased (about twice the normal level). After separation of the erythrocytes according to age by discontinuous Percoll density centrifugation, the pyruvate kinase activity was found to be increased in all Percoll fractions. Pyruvate kinase of the patient's cells was characterized by a decreased K0.5 for the substrate phosphoenolpyruvate and no inhibition by ATP. The Michaelis constant (Km) value for ADP, the nucleotide specificity, the thermostability, pH optimum, and immunological specific activity were normal. It is concluded that the high pyruvate kinase activity is due to a shift in the R(elaxed) in equilibrium T(ight) equilibrium to the R(elaxed) form.

2,3-Diphosphoglycerate↗
PubMed1984

Changes in activities and isozyme patterns of glycolytic enzymes during erythroid differentiation in vitro.

Late committed progenitor cells of erythropoiesis, CFU-E (colony-forming unit--erythroid), were isolated from mouse spleens to near homogeneity by a three-step enrichment procedure. The procedure included a four-day pretreatment of bled mice with the antibiotic thiamphenicol, a recovery period of 3 1/2 days, followed by centrifugal elutriation and Percoll density gradient centrifugation of the spleen cells. This practically pure CFU-E population was used to study some aspects of erythroid differentiation in vitro. Colony growth, as well as morphology and glycolytic enzyme activities of cells isolated at selected times of the 48-hour culture period, were determined. Marked declining activities of several enzymes, including hexokinase, phosphofructokinase, aldolase, enolase, pyruvate kinase, and glucose-6-phosphate dehydrogenase, were observed during in vitro differentiation. The activity of diphosphoglycerate mutase was almost absent in the CFU-E, but progressively increased during differentiation. The isozyme distribution of aldolase and enolase did not change during CFU-E in vitro differentiation into the reticulocyte. Hexokinase (HK) in the CFU-E contained mainly a double-banded type I isozyme, in addition to a minor amount of HK II. During differentiation, a shift was noticed within the double-banded HK I region, whereas HK ii disappeared after one cell division. Pyruvate kinase in the CFU-E was characterized by the presence of both the K-type and the L-type isozyme and hybrids of these isozyme types. During in vitro differentiation, the production of the K-type isozyme rapidly stops in favor of the L type.

Animals↗
PubMed1984

Glucose-6-phosphate isomerase deficiency-Nahariya: extreme in vitro and in vivo lability of the mutant enzyme.

A glucose-6-phosphate isomerase deficiency is described in an Arab boy suffering from chronic hemolytic anemia. The patient was probably true homozygous for the defect. The residual enzyme activity in his red blood cells (RBC) was approximately 30% of normal. The most striking enzyme abnormality observed was an extreme heat lability: upon incubation at 45 C, greater than 90% of activity was lost within 15 min. Furthermore, an increased affinity for the substrate glucose-6-phosphate was shown. The lability of the enzyme was also shown to exist in vivo by separating the patient's RBC into four fractions of different cell age by centrifugation on a discontinuous density gradient. This in vivo lability of the enzyme is believed to be the main cause of the hemolytic diathesis. Remarkably, the residual activity of the enzyme in the RBC of obligate heterozygotes was comparable to that in the patient. However, their enzyme activity was only slightly more labile than that in normal RBC and consequently no signs of hemolysis were noticed.

Anemia, Hemolytic↗
PubMed1983

Gas-chromatographic determination of cholesterol sulfate in plasma and erythrocytes, for the diagnosis of recessive X-linked ichthyosis.

We describe a rapid method for determining cholesterol sulfate in plasma and erythrocytes. After its single-step isolation by means of anion-exchange chromatography cholesterol sulfate is hydrolyzed, trimethylsilylated, and determined by gas chromatography with flame ionization detection. 5 beta-Cholestan-3 alpha-ol sulfate is used as internal standard. The method enables simultaneous determination of dehydroepiandrosterone sulfate in plasma. We applied it for the diagnosis of seven patients with recessive X-linked ichthyosis. Concentrations are given for plasma and erythrocytes from four unaffected relatives of patients with X-linked ichthyosis, a patient with placental sulfatase deficiency, two patients with other types of ichthyoses, and 20 controls. The method may also be of use for the rapid isolation of other organic sulfates from biological material, as illustrated by a comparison of gas chromatograms of urine from a normal pregnant woman and that from a patient with placental sulfatase deficiency.

Adolescent↗
PubMed1983

Glycolytic enzymes of an erythroleukemic cell line, K562, before and after hemoglobin induction.

The enzyme activities and isozyme distribution of some glycolytic enzymes were studied in the K562 cell line before and after induction of hemoglobin formation. Special attention was paid to the three regulator enzymes of glycolysis, hexokinase, phosphofructokinase and pyruvate kinase. Results for the K562 cell line were compared with those for the mature red cell. K562 cells exhibit a relatively low phosphofructokinase and high pyruvate kinase activity. Electrophoresis of hexokinase shows the presence of two bands in the HK I region. HK II is also present, probably as a result of culture conditions. Only 15% of the total hexokinase activity is mitochondrial bound. Phosphofructokinase in K562 cells is mainly composed of the L- and F-types of which the F-type is characteristic for platelets and granulocytes and not for erythrocytes. In the electrophoretic pattern of pyruvate kinase a predominant K4 band besides three hybrids were found. The hybrids were demonstrated to contain L-type subunits of pyruvate kinase, which means a new erythroid marker of K562 cells, as the red cell is the only blood cell that contains L-type pyruvate kinase. Induction experiments with hemin, ARA-C and mitomycin-C gave rise to more than 85% benzidine positive cells after 11 days of culture. The isozyme composition of pyruvate kinase did not change after induction. HK II disappears after induction with ARA-C and mitomycin-C but not with hemin. The results support the idea of the multipotential features of the K562 cell line.

Animals↗