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Biomedical subjects

S Eriksson

Publications and source records attributed to S Eriksson.

At least 37 records · Page 2Linked to original sources
PubMed2002

Effects of an implemented care policy on patient and personnel experiences of care.

A care policy was implemented within health care in the county of Västerbotten, Sweden. A questionnaire was administered before and after the implementation of the care policy to assess its effects. Patients within hospital care and primary health care described their experiences in a base-line study (n=3950) in 1994 and a follow-up study (n=2941) in 1996. On the same occasions personnel (n=2362 and 2310, respectively) answered the same questionnaire assessing what they thought their patients experienced. No significant positive effects of the implementation were seen by the patients. Fewer patients felt that they were understood when they talked about their problems, dared to express criticism or denied they were treated nonchalantly in the follow-up study. The experiences of the personnel were in line with those of the patients concerning nonchalant treatment in the follow-up study. Furthermore, fewer staff members thought that their patients felt they had adequate help with hygiene whilst more thought that their patients felt they were responded to in a loving way. One interpretation of the negative outcome is that organizational changes, strained resources and cuts in staffing during the 90s may have reduced the possibility of integrating the care policy in spite of an ambitious and extensive intervention.

Adult↗
PubMed2001

Modifying the cellular transport of DNA-based vaccines alters the immune response to hantavirus nucleocapsid protein.

Puumala virus is a member of the hantavirus genus (family Bunyaviridae) and is one of the causative agents of hemorrhagic fever with renal syndrome (HFRS) in Europe. A genetic vaccination approach was conducted to investigate if the immune response could be modulated using different cellular secretion and/or localisation signals, and the immune responses were analysed in BALB/c mice and in a bank vole infectious model. Rodents vaccinated with DNA constructs encoding the antigen fused to an amino-terminal secretion signal raised significantly higher antibody levels when compared to using constructs lacking secretion signals. Furthermore, the ratios of the IgG subclasses (IgG2a/IgG1) were raised by the use of cellular localisation signals, indicating a more pronounced Th1-type of immune response. The majority of the mice, or bank voles, immunised with DNA encoding a secreted form of the antigen showed a positive lymphoproliferative response and were protected against challenge with Puumala virus (strain Kazan-wt).

Animals↗
PubMed2001

Bovine cytosolic 5'-nucleotidase acts through the formation of an aspartate 52-phosphoenzyme intermediate.

Cytosolic 5'-nucleotidase/phosphotransferase (cN-II), specific for purine monophosphates and their deoxyderivatives, acts through the formation of a phosphoenzyme intermediate. Phosphate may either be released leading to 5'-mononucleotide hydrolysis or be transferred to an appropriate nucleoside acceptor, giving rise to a mononucleotide interconversion. Chemical reagents specifically modifying aspartate and glutamate residues inhibit the enzyme, and this inhibition is partially prevented by cN-II substrates and physiological inhibitors. Peptide mapping experiments with the phosphoenzyme previously treated with tritiated borohydride allowed isolation of a radiolabeled peptide. Sequence analysis demonstrated that radioactivity was associated with a hydroxymethyl derivative that resulted from reduction of the Asp-52-phosphate intermediate. Site-directed mutagenesis experiments confirmed the essential role of Asp-52 in the catalytic machinery of the enzyme and suggested also that Asp-54 assists in the formation of the acyl phosphate species. From sequence alignments we conclude that cytosolic 5'-nucleotidase, along with other nucleotidases, belong to a large superfamily of hydrolases with different substrate specificities and functional roles.

5'-Nucleotidase↗
PubMed2001

Deoxynucleoside anabolic enzyme levels in acute myelocytic leukemia and chronic lymphocytic leukemia cells.

The deoxynucleoside kinase reaction is often rate-limiting in the anabolism of pharmacologically active anti-cancer nucleosides. The levels of thymidine kinase (TK), deoxycytidine kinase, deoxyguanosine kinase (dGK), and thymidylate kinase were determined in leukocyte extracts from patients with chronic lymphocytic leukemia (CLL) and acute myelocytic leukemia (AML). The extracts from AML patients showed significantly higher TK activity than the ones from CLL patients. There were no differences in the levels of the other three kinases. In the case of dGK, the determinations were carried out with both an immunoblotting assay and selective enzyme activity measurements.

Blotting, Western↗
PubMed2001

Apoptosis induces efflux of the mitochondrial matrix enzyme deoxyguanosine kinase.

Deoxyguanosine kinase (dGK) initiates the salvage of purine deoxynucleosides in mitochondria and is a key enzyme in mitochondrial DNA precursor synthesis. The active form of the enzyme is a 60-kDa protein normally located in the mitochondrial matrix. Here we describe the subcellular distribution of dGK during apoptosis in human epithelial kidney 293 cells and human lymphoblast Molt-4 cells. Immunological methods were used to monitor dGK as well as other mitochondrial proteins. Surprisingly, dGK was found to relocate to the cytosolic compartment at a similar rate as cytochrome c, a mitochondrial intermembraneous enzyme known to enter the cytosol early in apoptosis. The redistribution of dGK from the mitochondria to the cytosol may be of importance for the activation of apoptotic purine nucleoside cofactors such as dATP and demonstrates that mitochondrial matrix proteins may selectively leak out during apoptosis.

Apoptosis↗
PubMed2001

Activation of deoxycytidine kinase by inhibition of DNA synthesis in human lymphocytes.

Deoxycytidine kinase (dCK, EC.2.7.1.74) is a key enzyme in the intracellular metabolism of 2-chlorodeoxyadenosine, 1-beta-D-arabinofuranosylcytosine, difluorodeoxycytidine, and other drugs used in chemotherapy of different leukaemias and solid tumours. Recently, stimulation of dCK activity was shown by these analogues and by other genotoxic agents such as etoposide and NaF, all of which cause severe inhibition of DNA synthesis in cell cultures. Here we describe that direct inhibition of DNA polymerases by aphidicolin stimulated dCK activity in normal lymphocytes and acute myeloid leukaemic cells, as well as in HL 60 promyelocytic cell cultures. Increased dCK activity was not due to new protein synthesis under our conditions, as measured by immunoblotting. Partial purification by diethylaminoethyl-Sephadex chromatography revealed that the activated form of dCK survived purification procedure. Moreover, it was possible to inactivate purified dCK preparations by recombinant protein phosphatase with Ser/Thr/Tyr dephosphorylating activity. These data suggest that the activation of dCK may be due to phosphorylation, and that deoxynucleoside salvage is promoted during inhibition of DNA synthesis in human lymphocytes.

Aphidicolin↗
PubMed2001

Human platelet calcium mobilisation in response to beta-amyloid (25-35): buffer dependency and unchanged response in Alzheimer's disease.

In the present study, the effects of beta-amyloid (25-35) (Abeta (25-35)) upon calcium signalling by the human platelet has been investigated. When assays were conducted using HEPES buffers, Abeta (25-35), but not the inactive peptide Abeta (35-25), produced a robust increase in intracellular calcium that remained after removal of extracellular calcium but was abolished by the phospholipase C inhibitor U-73122. There was no significant difference between the calcium response to Abeta (25-35) in platelets from patients with Alzheimer's disease and from age-matched controls. In contrast to the robust effects on calcium mobilisation in HEPES buffers, very little calcium response to Abeta (25-35) was seen when Krebs (pH 7.8) buffer was used.

Adult↗
PubMed2001

Losartan increases renal blood flow during isoflurane anesthesia in sheep.

BACKGROUND: Inhaled anesthetics cause a transient reversible depression of renal function by direct renal effects or indirectly by changes in neurohumoral systems or cardiovascular performance. When the sympathetic nervous activity is decreased during anesthesia, other vasoactive systems like vasopressin (AVP) and particularly the renin angiotensin system (RAS) are of importance for blood pressure maintenance. Little is known about how the renal circulation is affected by angiotensin receptor blockade during isoflurane anesthesia. METHODS: The study was performed on isoflurane anesthetized sheep equipped with flow probes (placed around a femoral and a renal artery) and a pulmonary artery catheter. During stable conditions the sheep were given one or more of the following substances: isotonic saline (NaCl); losartan (LOS) 10 mg x kg(-1); prazosin (PRAZ) 0.2 mg x kg(-1) and a vasopressin V1-receptor antagonist (AVP-a) 10 microg x kg(-1). RESULTS: LOS and AVP-a did not affect mean arterial pressure (MAP), whereas PRAZ lowered MAP significantly (from 98+/-12 to 65+/-7 mmHg). Renal blood flow (RBF) increased after LOS treatment (148+/-34 to 222+/-33 ml x min(-1)). The other substances were without effect on RBF. Femoral blood flow remained unchanged after all treatments. CONCLUSION: We conclude that the sympathoadrenal system is still the major determinant for blood pressure maintenance during isoflurane anesthesia in sheep. The apparently increased activity of the renin angiotensin system in this situation causes a reduction in renal blood flow, which is counteracted by angiotensin II AT1-receptor blockade.

Anesthesia↗
PubMed2001

Structural basis for substrate specificities of cellular deoxyribonucleoside kinases.

Deoxyribonucleoside kinases phosphorylate deoxyribonucleosides and activate a number of medically important nucleoside analogs. Here we report the structure of the Drosophila deoxyribonucleoside kinase with deoxycytidine bound at the nucleoside binding site and that of the human deoxyguanosine kinase with ATP at the nucleoside substrate binding site. Compared to the human kinase, the Drosophila kinase has a wider substrate cleft, which may be responsible for the broad substrate specificity of this enzyme. The human deoxyguanosine kinase is highly specific for purine substrates; this is apparently due to the presence of Arg 118, which provides favorable hydrogen bonding interactions with the substrate. The two new structures provide an explanation for the substrate specificity of cellular deoxyribonucleoside kinases.

Adenosine Triphosphate↗
PubMed2001

The deoxyguanosine kinase gene is mutated in individuals with depleted hepatocerebral mitochondrial DNA.

Mitochondrial DNA (mtDNA)-depletion syndromes (MDS; OMIM 251880) are phenotypically heterogeneous, autosomal-recessive disorders characterized by tissue-specific reduction in mtDNA copy number. Affected individuals with the hepatocerebral form of MDS have early progressive liver failure and neurological abnormalities, hypoglycemia and increased lactate in body fluids. Affected tissues show both decreased activity of the mtDNA-encoded respiratory chain complexes (I, III, IV, V) and mtDNA depletion. We used homozygosity mapping in three kindreds of Druze origin to map the gene causing hepatocerebral MDS to a region of 6.1 cM on chromosome 2p13, between markers D2S291 and D2S2116. This interval encompasses the gene (DGUOK) encoding the mitochondrial deoxyguanosine kinase (dGK). We identified a single-nucleotide deletion (204delA) within the coding region of DGUOK that segregates with the disease in the three kindreds studied. Western-blot analysis did not detect dGK protein in the liver of affected individuals. The main supply of deoxyribonucleotides (dNTPs) for mtDNA synthesis comes from the salvage pathway initiated by dGK and thymidine kinase-2 (TK2). The association of mtDNA depletion with mutated DGUOK suggests that the salvage-pathway enzymes are involved in the maintenance of balanced mitochondrial dNTP pools.

Base Sequence↗
PubMed2001

Mutant mitochondrial thymidine kinase in mitochondrial DNA depletion myopathy.

The mitochondrial deoxyribonucleotide (dNTP) pool is separated from the cytosolic pool because the mitochondria inner membrane is impermeable to charged molecules. The mitochondrial pool is maintained by either import of cytosolic dNTPs through dedicated transporters or by salvaging deoxynucleosides within the mitochondria; apparently, enzymes of the de novo dNTP synthesis pathway are not present in the mitochondria. In non-replicating cells, where cytosolic dNTP synthesis is down-regulated, mtDNA synthesis depends solely on the mitochondrial salvage pathway enzymes, the deoxyribonucleosides kinases. Two of the four human deoxyribonucleoside kinases, deoxyguanosine kinase (dGK) and thymidine kinase-2 (TK2), are expressed in mitochondria. Human dGK efficiently phosphorylates deoxyguanosine and deoxyadenosine, whereas TK2 phosphorylates deoxythymidine, deoxycytidine and deoxyuridine. Here we identify two mutations in TK2, histidine 90 to asparagine and isoleucine 181 to asparagine, in four individuals who developed devastating myopathy and depletion of muscular mitochondrial DNA in infancy. In these individuals, the activity of TK2 in muscle mitochondria is reduced to 14-45% of the mean value in healthy control individuals. Mutations in TK2 represent a new etiology for mitochondrial DNA depletion, underscoring the importance of the mitochondrial dNTP pool in the pathogenesis of mitochondrial depletion.

Base Sequence↗
PubMed2001

Effects of losartan, prazosin and a vasopressin V1-receptor antagonist on renal and femoral blood flow in conscious sheep.

The regulation of blood flow to different organs is determined by the autonomic nervous system and systemic and/or local vasoactive substances. Although the cardiovascular effects of the renin-angiotensin system (RAS), the sympathoadrenal system and vasopressin (AVP) have been thoroughly studied, there are relatively few investigations on these systems with concomitant measurements of systemic haemodynamics and regional blood flow in conscious unstressed individuals. We therefore studied effects of pharmacological blockade of AVP V1-, angiotensin II (ANG II) AT1-and adrenergic alpha-receptors on central and regional (renal and femoral blood flow) haemodynamics in adult conscious ewes. Eight adult cross-bred ewes were chronically intrumented with peri-vascular ultrasonic flow probes implanted unilaterally around the renal and the femoral artery. While standing in their habitual environment, systemic and regional haemodynamics were measured before and after the following treatments as single intravenous injections. Animals in group A (n = 6) were given isotonic saline (NaCl) followed by the AT1-receptor blocker losartan (LOS, 10 mg kg-1) 30 min later; group B (n = 6) animals were given the alpha-adrenoceptor blocker prazosin (PRAZ, 0.2 mg kg-1); and group C (n = 6) the vasopressin V1 receptor antagonist [d(CH2)5Tyr(Me)AVP] (AVP-a, 10 microg kg-1). PRAZ reduced mean arterial pressure (MAP) by 11% concomitant with an increase in heart rate (HR) (32%), whereas the other substances where without effect on those variables. Femoral blood flow (FBF) was enhanced (increased by 82%) by injection of PRAZ only. Administration of LOS increased the renal blood flow (RBF) by 11% while the other drugs were without effect on that parameter. We conclude that basal renal vascular tone in conscious unstressed sheep is dependent on angiotensinergic mechanism and that blockade of this influence causes a local increase in flow without concomitant effects on systemic haemodynamics.

Angiotensin Receptor Antagonists↗
PubMed2001

Pharmacological basis for cladribine resistance in a human acute T lymphoblastic leukaemia cell line selected for resistance to etoposide.

Cross-resistance between different classes of anti-neoplastic agents can jeopardize successful combination cancer chemotherapy. In this study, we observed an unexpected cross-resistance between the podophyllotoxine derivative etoposide (VP) and the nucleoside analogue cladribine (CdA) in CCRF-CEM cells developed for resistance to VP. The resistant cells also displayed 14- and twofold resistance to cytarabine (ara-C) and gemcitabine respectively. Closer analysis of these cells showed that they contained lower amounts of topoisomerase (topo) IIalpha (P < 0.001) and beta protein (P < 0.026), formed substantially lower amounts of the topo II-DNA complex, and had a markedly decreased level of Fas (CD95/APO-1)-ligand mRNA expression. Interestingly, Fas expression in the resistant cells did not differ from that in the parental cell line. No differences were observed in the accumulation/efflux of daunorubicin or in the gene expressions of P-glycoprotein, multidrug resistance-associated protein and the lung resistance-related protein. The activity of deoxycytidine kinase (dCK), responsible for activation of CdA and ara-C, was the same for resistant and wild-type cells. However, there was an increase in the activity of the cytosolic 5'-nucleotidases (5'-NT), responsible for deactivation of nucleotides, amounting to 206% (P < 0.001) for the high Km and 134% (P < 0.331) for the low Km 5'-NT in resistant cells. The high Km 5'-NT is probably responsible for the decreased amount of the active metabolite CdA 5'-triphosphate [40% decreased (P < 0.045)], as well as for other purine ribonucleosides and deoxyribonucleosides triphosphates in the resistant cells. In contrast, a significantly higher deoxycytidine triphosphate (dCTP) level (167%, P < 0.001) was observed in the resistant cells. Thus, this study suggests that the major cause of resistance to the nucleoside analogues CdA and ara-C in cells selected for resistance to VP is a result of metabolic alterations producing increased activity of 5'-NT and higher dCTP levels. Furthermore, these results indicate that there is a common factor in the regulation of nucleotide-degrading enzymes and DNA topoisomerases, which may be altered in cross-resistant cells.

5'-Nucleotidase↗
PubMed2001

Cross-resistance to cytosine arabinoside in a multidrug-resistant human promyelocytic cell line selected for resistance to doxorubicin: implications for combination chemotherapy.

The pyrimidine analogue cytosine arabinoside (AraC) is one of the most effective drugs used in the treatment of acute leukaemia. Overexpression of the multidrug resistance (MDR-1) gene and its product, P-glycoprotein (P-gp), is associated with cellular resistance to drugs, such as anthracyclines and vinca alkaloids. This resistance can be reversed by cyclosporine analogues or verapamil (ver). We investigated the in vitro cross-resistance to AraC in a doxorubicin-resistant HL60 cell line, with an elevated expression of the MDR-1 gene. The resistant clone showed an eightfold increased resistance to AraC and a two- to fourfold resistance to the other analogues, as measured by cytotoxicity test. There was no significant increase in the activity of 5'-nucleotidase or in the amount of deoxyribonucleotide pools between cell lines. We could, however, detect a reduction in deoxycytidine kinase (dCK) activity (30%, P = 0.021, using deoxycytidine as substrate) and the level of AraC triphosphates was significantly reduced in the resistant cells (70%, P = 0.009). When the cells were exposed to cyclosporin A (CsA) or the cyclosporine analogue PSC 833 (PSC) in combination with AraC, there was more extensive apoptosis, as measured by formation of oligonucleosomal DNA fragmentation and caspase-3-like activity, than with exposure to AraC alone. We also found an increased retention of AraC in the resistant cells when incubated with AraC in combination with CsA. Ver in combination with AraC, failed to increase apoptosis for the resistant cell line. Our data suggests that the resistance to AraC for the P-gp-expressing cells is a result of a reduction of dCK activity and an increase in efflux, the latter possibly depending on P-gp. A combination of CsA or PSC with AraC may improve the effect of AraC in vivo.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2001

Evaluation of various electrocardiographic criteria for left ventricular hypertrophy in patients with stable angina pectoris: influence of using modified limb electrodes.

BACKGROUND: Left ventricular hypertrophy (LVH) in coronary heart disease is associated with poor prognosis. Electrocardiography (ECG) criteria for LVH, when using ECG with modified limb electrode positions, has not been validated in patients with angina pectoris. METHODS: Echocardiography and resting ECGs with modified limb electrode positions, i.e. with the limb leads placed on the abdomen instead of the extremities, were registered from 468 patients (295 men) with stable angina pectoris. To evaluate the influence of using modified limb electrode positions, ECGs with standard and modified limb electrode positions were compared in a control group consisting of 50 other patients. RESULTS: The ECG criteria for LVH according to the Perugia score, the Minnesota code and Romhilt & Estes reached the highest sensitivity values, 27-31% in men and 24-38% in women, while the sensitivities of different Cornell criteria were as low as 6-10% in men and 19-29% in women. In the control group, the R- and S-wave amplitudes of the precordial leads were only slightly changed, as expected, whereas those of the limb leads changed considerably. Based on these results, we corrected aVL in the main study, which increased the sensitivity of the Cornell voltage criteria from 15 to 30%, while the specificity was maintained at 95%. CONCLUSIONS: ECGs registered with modified limb electrode positions can be used to detect LVH with traditional ECG criteria, but changes in the limb leads are considerable and influence the sensitivities.

Abdomen↗
PubMed2001

Novel deoxynucleoside-phosphorylating enzymes in mycoplasmas: evidence for efficient utilization of deoxynucleosides.

Mycoplasmas are unable to synthesize purine and pyrimidine bases de novo. Therefore, salvage of existing nucleosides and bases is essential for their survival. Four mycoplasma species were studied with regard to their ability to phosphorylate deoxynucleosides. High levels of thymidine kinase (TK), deoxycytidine kinase (dCK), deoxyguanosine kinase (dGK) and deoxyadenosine kinase (dAK) activities were detected in extracts from Mycoplasma pneumoniae, Mycoplasma mycoides subsp. mycoides SC (M. mymySC), Acholeplasma laidlawii (A. laidlawii) and Mycoplasma arginini (M. arginini). Nucleoside phosphotransferase activities were found at high levels in A. laidlawii and low levels in M. arginini. Pyrophosphate-dependent deoxynucleoside kinase activities were detected mainly in A. laidlawii and M. mymySC extracts. Two open reading frames were identified in the M. mymySC genome; one showed 25% sequence identity to human dGK and the other one had about 26% sequence identity to human TK1. The M. mymySC dGK-like enzyme was cloned, expressed in Escherichia coli and affinity-purified. This enzyme phosphorylated dAdo, dGuo and dCyd, and the highest catalytic rate was with dAdo as substrate. Therefore, we suggest that this enzyme should be named deoxyadenosine kinase. The physiological role of mycoplasma dAK and TK may be to support the unusually large dATP and dTTP pools required for replication of mycoplasma genomes.

Amino Acid Sequence↗
PubMed2001

Purification and characterization of myrosinase from the cabbage aphid (Brevicoryne brassicae), a brassica herbivore.

Aphids are among the most serious insect pests of agricultural crops in the world. They often have specific hosts, and the cabbage aphid (Brevicoryne brassicae) is a specialist on Cruciferae. It has previously been described that certain insects contain the enzyme myrosinase (EC 3.2.3.1), which is considered an important defence enzyme of crucifers. Myrosinase was purified to homogeneity from cabbage aphid soluble extracts using anion-exchange and phenyl-Sepharose chromatography. The protein has an apparent subunit molecular mass of 57-58 kDa and is a dimer. The isoelectric point is 4.9 and the enzyme has a temperature optimum around 40 degrees C. The enzyme was active towards the glucosinolates tested, sinigrin and glucotropaeolin, but was inhibited by ascorbate at concentrations that normally activate plant myrosinases. Using sinigrin as the substrate Km was determined as 0.41 mM, and the kcat as 36 s(-1). With glucotropaeolin the Km and kcat values were determined as 0.52 mM and 22.8 s(-1), respectively. The enzyme was stable upon storage at 4 degrees C for many months, but lost some activity upon freezing. The insect myrosinase did not cross-react with antibodies raised to plant myrosinase. Peptide sequencing of a tryptic digest of the protein showed homology to beta-glucosidases. The presence of myrosinase in an insect pest specialist may be an example of a coevolution process that facilitates host specialization.

Amino Acid Sequence↗