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Biomedical subjects

S Eriksson

Publications and source records attributed to S Eriksson.

At least 19 recordsLinked to original sources
PubMed1992

Selective assays for thymidine kinase 1 and 2 and deoxycytidine kinase and their activities in extracts from human cells and tissues.

Human cells salvage pyrimidine deoxyribonucleosides via 5'-phosphorylation which is also the route of activation of many chemotherapeutically used nucleoside analogs. Key enzymes in this metabolism are the cytosolic thymidine kinase (TK1), the mitochondrial thymidine kinase (TK2) and the cytosolic deoxycytidine kinase (dCK). These enzymes are expressed differently in different tissues and cell cycle phases, and they display overlapping substrate specificities. Thymidine is phosphorylated by both thymidine kinases, and deoxycytidine is phosphorylated by both dCK and TK2. The enzymes also phosphorylate nucleoside analogs with very different efficiencies. Here we present specific radiochemical assays for the three kinase activities utilizing analogs as substrates that are by more than 90 percent phosphorylated solely by one of the kinases; i.e. 3'-azido-2',3'-dideoxythymidine (AZT) as substrate for TK1, 1-beta-D-arabinofuranosylthymidine (AraT) for TK2 and 2-chlorodeoxyadenosine (CdA) for dCK. We determined the fraction of the total deoxycytidine and thymidine phosphorylating activity that was provided by each of the three enzymes in different human cells and tissues, such as resting and proliferating lymphocytes, lymphocytic cells of leukemia patients (chronic lymphocytic, chronic myeloic and hairy cell leukemia), muscle, brain and gastrointestinal tissue. The detailed knowledge of the pyrimidine deoxyribonucleoside kinase activities and substrate specificities are of importance for studies on chemotherapeutically active nucleoside analogs, and the assays and data presented here should be valuable tools in that research.

Arabinonucleosides↗
PubMed1992

The HIV replication inhibitor 3'-fluoro-3'-deoxythymidine blocks sialylation of N-linked oligosaccharides.

The ability of 3'-fluoro-3'-deoxythymidine (FLT) to interfere with glycosylation was investigated in an experimental system, where the effects on the herpes simplex virus type 1-specified glycoprotein gC were determined. By adding FLT to HSV-infected cells after the peak of DNA synthesis, it was possible to segregate possible effects on nucleic acid metabolism from the effects on glycosylation of gC. It was found that FLT treatment of HSV-infected cells at concentrations of 20-500 micrograms/ml resulted in a significant increase in the electrophoretic mobility of gC, indicating a reduction of the amount of carbohydrates incorporated into gC. Lectin-binding assays demonstrated that the FLT treatment blocked addition of sialic acid to complex type N-linked glycans. The effects on glycosylation were observed in cells infected with an HSV mutant, deficient in thymidine kinase (TK), but not in cells infected with wild type virus. The cells infected with the wild type virus contained five times more total FLT metabolites than the cells infected with the TK-deficient mutant, whereas the latter cell type contained significantly higher amounts of unmetabolized FLT. This result indicates that FLT itself, and not a metabolite, was responsible for the effects on glycosylation.

Antibodies, Monoclonal↗
PubMed1992

Thymidine and 3'-azido-3'-deoxythymidine metabolism in human peripheral blood lymphocytes and monocyte-derived macrophages. A study of both anabolic and catabolic pathways.

3'-Azido-3'-deoxythymidine (AZT) is HIV-inhibitory in human macrophages, which is surprising in view of the low AZT phosphorylation reported in macrophage extracts. To elucidate the mechanism of AZT activation, we studied AZT anabolism as well as catabolism in human lymphocytes and macrophages, and compared it to that of thymidine. Thymidine kinase (TK)-specific activity in mitogen-stimulated lymphocytes was 15 times higher than in macrophages. However, the TK activity per cell was only 1.3 times higher, because of the large macrophage cell volume. Total cellular TK activity, but not specific activity, matched the level of intracellular AZT anabolism. The substrate specificity of TK in macrophages strongly suggests that mitochondrial TK2 was the enzyme phosphorylating thymidine and AZT in these cells, whereas it was cytosolic TK1 in stimulated lymphocytes. In vivo thymidine catabolism was extensive, forming thymine and dihydrothymine. In macrophages more than 95% of the added thymidine (0.5 microM) was degraded within 60 min. AZT, in contrast, was not catabolized, which explains the high AZT nucleotide accumulation, a process opposed only by AZTMP excretion. The lack of catabolism together with phosphorylation by TK2 clarifies how AZT can inhibit human immunodeficiency virus in macrophages. The fact that TK2 and not TK1 phosphorylates AZT in macrophages should have important implications for combination chemotherapy.

Chromatography, High Pressure Liquid↗
PubMed1992

Mammalian thymidine kinase 2. Direct photoaffinity labeling with [32P]dTTP of the enzyme from spleen, liver, heart and brain.

Thymidine kinase 2 (TK2), also called mitochondrial thymidine kinase, is a pyrimidine deoxyribonucleoside kinase expressed in all cells and tissues. It was recently purified to apparent homogeneity from human leukemic spleen and the active enzyme was shown to be a monomer of a 29-kDa polypeptide. The enzyme is feedback-inhibited by both end products, dCTP and dTTP. Here we show that TK2 purified from several different sources, including purified beef heart mitochondria, could be directly photoaffinity labeled with radioactive dTTP (approximately 18% of all TK2 molecules were cross-linked to dTTP after 20 min of ultraviolet irradiation) or to a lower extent with dCTP. Photo-incorporation was inhibited by the presence of the other effector but also the phosphate donor ATP blocked photolabeling, with dTTP. Addition of nucleoside substrates gave only a marginal inhibition of photo-incorporation. There were no detectable difference in the molecular size of photolabeled TK2 isolated from human spleen, brain or placenta, monkey liver, beef heart and beef heart mitochondria. Nor was there any significant differences in the enzyme kinetic properties of these enzymes. Cleavage of labeled TK2 with cyanogen bromide showed that dTTP was incorporated into a single 3-kDa peptide. TK2 was the only pyrimidine deoxynucleoside kinase expressed in liver, heart and brain. A detailed characterization of the subunit structure and substrate specificity of this enzyme is of importance for the design of new antiviral and cytostatic therapies based on nucleoside analogs.

Affinity Labels↗
PubMed1992

Substrate specificity of human deoxycytidine kinase toward antiviral 2',3'-dideoxynucleoside analogs.

Deoxycytidine (dCyd) kinase has been purified to homogeneity from human leukemic spleen, and the capacity of the enzyme to phosphorylate 2',3'-dideoxynucleoside (ddN) analogs that are clinically effective inhibitors of human immunodeficiency virus (HIV) replication was evaluated. Cytosine-containing ddN analogs, such as 2',3'-dideoxycytidine, 2',3'-dideoxy-2',3'-dehydrocytidine, and cytallene, were efficiently phosphorylated by dCyd kinase, while no phosphorylation of purine-containing ddN analogs was detected. dCyd kinase was completely inactive toward 2',3'-dideoxyadenosine (ddAdo), 2',3'-dideoxyinosine, 2',3'-dideoxyguanosine, and adenallene, although it was capable of phosphorylating both 2'-deoxyadenosine (dAdo) and 2'-deoxyguanosine (dGuo). The abilities of wild type and mutant human T lymphoblastoid CEM cells to accumulate ddAdo in situ and in vitro were also ascertained. Comparison of the abilities of intact wild type CEM cells and derivatives deficient in nucleoside transport, dCyd kinase, and/or adenosine (Ado) kinase to accumulate [3H]ddAdo-derived radioactivity revealed no significant differences among the wild type and mutant strains. However, ddAdo phosphorylating activity was decreased in extracts from Ado kinase-deficient cells but not in lysates prepared from cells genetically deficient in dCyd kinase activity. In comparative growth rate experiments, wild type, nucleoside transport-deficient, and dCyd kinase-deficient CEM cells were equally sensitive to ddAdo toxicity, while, interestingly, a deficiency in Ado kinase correlated with a 5-fold decreased growth sensitivity to the purine ddN. Insertion of an adenine phosphoribosyltransferase deficiency into the CEM cell lines did not influence ddAdo toxicity or incorporation rate. These results imply that Ado kinase may be an important factor in ddAdo phosphorylation by CEM cells. Furthermore, these studies demonstrate that cytosine- and purine-containing ddNs are transported and activated by independent pathways and, therefore, have important implications for anti-HIV therapy in that pyrimidine and purine ddNs might be used in combination for the treatment of acquired immunodeficiency syndrome.

Adenine Phosphoribosyltransferase↗
PubMed1992

Dynamics of benzo[a]pyrene diol epoxide adducts in poly(dG-dC).(dG-dC) studied by synchrotron excited fluorescence polarization anisotropy decay.

Time-resolved fluorescence studies have been performed on (+)-anti-7,8-dihydrodiol-9,10-epoxybenzo[a]pyrene adducts in double-stranded poly(dG-dC).(dG-dC). Part of the adduct population gives rise to excimer fluorescence. The heterogeneous fluorescence emission decay curves at 22 degrees C could be resolved into three components with lifetimes: 0.4 ns, 3 ns and 24 ns for the total fluorescence (monomer and excimer emission), and 0.5 ns, 5 ns and 24 ns, respectively, for excimer emission alone. The relative amplitudes for the longer lifetimes were larger for the pure excimer population than for the mixed population. The fluorescence polarization anisotropy decay curves were resolved into two components of rotational correlation times: 0.4 ns and 25 ns for the total fluorescence and 0.3 ns and 33 ns for the excimer fluorescence. We interpret the two rotational correlation times to correspond to local motion of the adduct and segmental motion of the polynucleotide, respectively.

Chemical Phenomena↗
PubMed1992

Thermogenic response to intravenous nutrition in patients with cirrhosis.

Energy expenditure was determined using continuous indirect calorimetry in the basal state and during 3 h of total parenteral nutrition (TPN) in 8 patients with cirrhosis and 8 healthy volunteers. TPN consisted of glucose, fat and amino acids and had a glucose/fat ratio of 50:50. The infusion rate was set to provide energy corresponding to 62.5% of the individually measured 24-h resting energy expenditure. In the basal state energy expenditure was similar in patients and controls while the respiratory quotient (RQ) was lower in the patients (0.78 +/- 0.01 vs. 0.82 +/- 0.01, mean +/- SEM, p < 0.05). During TPN, energy expenditure increased progressively during the 3-h infusion period. The average rise in energy expenditure was similar in patients (19.1 +/- 1.2%) and in controls (21.4 +/- 1.6%, n.s.). The RQ rose in both groups, but more in the patients with cirrhosis. At the end of the study, RQ was higher in patients (0.89 +/- 0.01) than in controls (0.85 +/- 0.01, p < 0.05). It is concluded that the nutrient-induced rise in energy expenditure during TPN is not significantly different in patients with cirrhosis and control subjects. Furthermore, the results indicate that the increased fat utilization in overnight fasting cirrhotic patients is rapidly shifted to an augmented carbohydrate oxidation during TPN, possibly as a consequence of marked hyperinsulinemia.

Adult↗
PubMed1992

Plexiform fibrohistiocytic tumor. Report of a case involving preoperative aspiration cytology and immunohistochemical and ultrastructural analysis of surgical specimens.

A typical case of plexiform fibrohistiocytic tumor (Enzinger and Zhang) occurring in the skin and subcutis of the abdominal wall in a 7-year-old girl is reported. Preoperative fine-needle aspiration cytology revealed a benign lesion with fibroblastic-histiocytic features which also contained bi- and multinucleated giant cells. The surgical specimen showed a tumor with multiple small nodules within fibrous septa; these nodules were composed of spindle cells and epithelioid cells and contained scattered multinucleated osteoclast-like cells. The tumor cells showed ultrastructural and immunohistochemical features of myofibroblasts and histiocyte-like cells. Thus, there was an abundance of lysosomes, prominent filopodia and bundles of thin cytofilaments along the cytoplasmic border, as well as immunoreactivity for alpha-smooth-muscle-specific actin, alpha-1-antitrypsin and alpha-1-antichymotrypsin. Ultrastructurally there were tumor cells exhibiting features of histiocytes which also contained bundles of actin of smooth muscle type. The presented case of plexiform fibrohistiocytic tumor appears to be composed of a rather peculiar cell form, somewhere between myofibroblasts and histiocytes.

Abdominal Neoplasms↗
PubMed1992

Hydroxyurea-induced cell death in human T lymphoma cells as related to imbalance in DNA/protein cycle and deoxyribonucleotide pools and DNA strand breaks.

The aim of this study was to elucidate the mechanism(s) behind the cellular toxicity of therapeutic concentrations of hydroxyurea (HU). Treatment of human T lymphoma cells (CCRF-CEM) with 60-100 microM of HU for 24 h decreased the growth rate by 90% due to accumulation of cells in early S phase. It induced a marked imbalance in both the DNA/protein cycle (as measured by two-parameter flow cytometry) and the deoxyribonucleotide (dNTP) pools. HU treatment did not enhance the frequency of DNA single-strand breaks (SSBs), as measured by the alkaline unwinding technique. Cell viability was unaffected. However, removal of HU led to 10-15% cell loss during the following 12 h period in parallel with increasing SSBs, and a rapid progression of cells through S and G2 stages. The unbalanced DNA to protein content per cell and the dNTP pools were normalized 6-12 and 24 h after removal of HU, respectively. These results show that marked changes in the DNA to protein ratio and dNTP pools alone are not directly lethal, but when combined with a high replicative DNA synthesis rate, as found after removal of HU, apparently lead to elevated cell death.

Cell Cycle↗
PubMed1992

Prednimustin treatment in primary biliary cirrhosis: a preliminary study.

We observed a decrease in serum bilirubin, alkaline phosphatases (ALP) and IgM in five patients with primary biliary cirrhosis (PBC) treated with Prednimustin (Sterecyt) for 6 months. In contrast to pretreatment findings, C3 activation was undetectable during treatment in three patients where normalization of serum IgM was achieved. After discontinuation of Prednimustin, bilirubin and ALP levels rapidly returned to pretreatment values, although IgM remained normal for up to 6 months in some patients. We conclude that Prednimustin might be of value in patients with symptomatic PBC where liver transplantation is not an option, and that it should be evaluated in a controlled study. However, the rapid reactivation of the disease after conclusion of treatment must be considered.

Aged↗
PubMed1992

Hepatitis C in chronic liver disease: an epidemiological study based on 566 consecutive patients undergoing liver biopsy during a 10-year period.

We analysed the presence of hepatitis C virus (HCV) antibodies in 566 patients undergoing liver biopsy. While over 20% of the patients were anti-HCV positive according to ELISA, only 13.8% had HCV antibodies when tested with a four-antigen recombinant immunoblot assay (RIBA 2). At the time of inclusion in the study, most patients were asymptomatic, irrespective of whether they were HCV-positive. Histological findings in anti-HCV-positive patients were chronic persistent hepatitis, chronic active hepatitis or cirrhosis in greater than 75% of cases. Only four of the patients who were anti-HCV-positive according to the RIBA 2 had autoimmune chronic active hepatitis. Risk behaviour could be identified in the majority of cases. Community-acquired sporadic cases were rare (12%). Of the 153 patients who died during follow-up, 23 subjects were anti-HCV positive. Although age- and sex-adjusted survival was not shorter in anti-HCV-positive patients than in anti-HCV-negatives, the risk of hepatocellular cancer was higher (P = 0.01). We conclude that HCV infection is associated with chronic liver disease, even when critical evidence of viral aetiology is slight. Truly sporadic cases are rare. Patients infected with HCV are at increased risk of developing hepatocellular cancer.

Adolescent↗
PubMed1992

A comparative study of the social conditions of spouses of long term patients cared for either in nursing homes or home care.

In order to study the social conditions of spouses of patients suffering from long term illnesses structured interviews were performed. The interviewees were divided into two groups: spouses of persons with chronic conditions cared for at home and spouses of patients cared for in nursing homes. Each group consisted of 27 spouses and there were no differences in physical health score, Mini mental score or ability to manage primary Activities of Daily Living functions between the groups. Home care spouses paid fewer visits to children, had fewer friends and paid fewer visits to friends and they also had time for hobbies or interests significantly more seldom (reading, visits to church) than nursing home spouses. There were no significant differences between the groups concerning sex, socio-economic class, housing conditions and amount of home health services. Their contact with children and their feelings of loneliness were reported to be the same.

Aged↗
PubMed1992

A controlled multicenter clinical study of citalopram and placebo in elderly depressed patients with and without concomitant dementia.

A total of 149 patients in 7 centers in Denmark, Norway and Sweden entered a 6-week double-blind trial intended to assess the antidepressant effect and safety of citalopram vs placebo in depressed elderly patients (65 years of age or older) who might also suffer from somatic disorders and/or senile dementia. Results of ratings on the Hamilton Rating Scale for Depression, the Montgomery-Asberg Depression Rating Scale and the Clinical Global Impression Scale provided consistent evidence that the citalopram-treated patients improved more than the placebo-treated patients. Results of ratings on the Gottfries-Bråne-Steen dementia rating scale indicated that both cognitive and emotional functioning improved significantly more in the citalopram-treated subgroup of patients with dementia than in the placebo-treated subgroup.

Aged↗
PubMed1992

Angiotensinogen in chronic liver disease.

The renin substrate angiotensinogen (AGT) belongs to a supergene family of proteins that also includes alpha 1-antitrypsin (AAT) and alpha 1-antichymotrypsin (ACT), acute-phase reactants with known serine proteinase inhibitory (serpin) function. AGT lacks a known inhibitory function but is an acute-phase reactant. In this study we have compared the plasma levels, as analysed by electroimmunoassay, of AGT with AAT in patients with different types of chronic liver disease. AAT levels are regularly elevated in liver disease patients in contrast to AGT, which remains normal until late in the disease course. The AGT levels (mean +/- SD) were: in alcoholic cirrhosis (n = 19) 100 +/- 27.3%, in chronic active hepatitis (n = 14) 100 +/- 23.2%, in primary biliary cirrhosis (n = 18) 106 +/- 26.1% and in non-alcoholic cirrhosis (n = 15) 92 +/- 38.4%. Only occasionally were levels less than 50% of normal seen. In general, AGT levels were unrelated to sex and type of underlying liver disease and did not correlate with degree of hepatocellular impairment. Crossed immunoelectrophoresis showed no abnormal charge heterogeneity of AGT in patients with low levels. Our data are consistent with a dissociate expression of the homologous serpin genes in chronic liver disease. We speculate that the magnitude of the dissociated response is influenced by hormonal factors.

Adolescent↗
PubMed1992

Lipoprotein(a) and acute-phase proteins in acute myocardial infarction.

Lipoprotein(a) (Lp(a)) and the acute-phase proteins, orosomucoid, haptoglobin and alpha 1-antitrypsin, were studied in 32 patients with acute myocardial infarction. Samples were taken at admission and, after fasting overnight, on the following 6 days. In a subgroup of 21 patients total serum cholesterol, high-density lipoprotein (HDL) cholesterol and triglycerides were also estimated. In a linear regression model a significant relation between the relative values of Lp(a) and the time in days was obtained (p = 0.001). Compared with the acute-phase proteins, however, Lp(a) showed a weak increase and the individual responses were very variable. There were no correlations between the individual changes in Lp(a) and the changes in the acute-phase proteins, but Lp(a) changes correlated significantly with the changes in total cholesterol and low-density lipoprotein (LDL) cholesterol. It is suggested that the Lp(a) reaction in myocardial infarction is linked to the reaction of the lipoproteins. There may also be several clinical conditions, including different medications, which influence the Lp(a) level.

Acute-Phase Proteins↗
PubMed1991

Deoxynucleoside phosphorylating enzymes in monkey and human tissues show great similarities, while mouse deoxycytidine kinase has a different substrate specificity.

Three key enzymes in the anabolic phosphorylation of deoxyribonucleosides and deoxyribonucleoside analogs were purified i.e. cytoplasmic thymidine kinase (TK1), mitochondrial thymidine kinase (TK2) and cytoplasmic deoxycytidine kinase (dCK) from human, mouse and monkey liver and spleen. Their subunit structure and substrate specificities were compared. Extensive purification of TK1 and dCK from mouse spleen and TK2 from mouse and monkey livers revealed major polypeptide bands of 25, 30 and 28 kD, respectively, on sodium dodecyl sulphate-polyacrylamide gel electrophoresis which are very similar to the subunit molecular weights of the corresponding human enzymes. Affinity purified polyclonal antibodies against human dCK also cross-reacted with 30 kD bands in extracts from both mouse and monkey spleen. Thus, the molecular weights of the subunits of these three enzymes appeared to be very similar in all three species. TK1 and TK2 from these different sources appeared to have similar substrate specificities against several deoxyribonucleoside analogs. However, mouse dCK differed significantly from monkey and human dCK in its capacity to phosphorylate dAdo and 2',3'-dideoxycytidine (ddCyd) with a Vmax approximately 10-fold lower than that of the two latter enzymes. The Km and Vmax values for dCyd and arabinocytosine appeared to be very similar with the enzymes from all three species. The fact that mouse dCK shows low activity with dAdo and ddCyd explains differences reported previously in the metabolism of dAdo and ddCyd in mouse compared to that in human lymphocytes. These results argue against the use of mice as model systems for human deoxynucleoside metabolism.

Animals↗