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Biomedical subjects

S Eriksson

Publications and source records attributed to S Eriksson.

At least 253 records · Page 14Linked to original sources
PubMed1993

Substrate specificity of mitochondrial 2'-deoxyguanosine kinase. Efficient phosphorylation of 2-chlorodeoxyadenosine.

Mitochondrial deoxyguanosine kinase (dGK) (EC 2.7.1.113) was purified to apparent homogeneity from bovine brain. The molecular mass of the native protein was 56 kDa, as judged by gel filtration, and one single band of 28 kDa was seen in sodium dodecyl sulfate-gel electrophoresis. 2'-Deoxyguanosine (dGuo) (Km, 7.6 microM), 2'-deoxyinosine, and 2'-deoxyadenosine (Km, 60 microM) were substrates for the enzyme as well as several dGuo analogs containing a lipophilic substituent at C-2'. Carbocyclic dGuo, 9-beta-D-arabinofuranosylguanine, 9-beta-D-arabinofuranosylhypoxanthine, and 9-beta-D-arabinofuranosyladenine were substrates for the enzyme, whereas no 3'-modified dGuo analogs were effective. Interestingly, 2-chloro-2'-deoxyadenosine (CdA) was found to be an efficient substrate for dGK (Km, 85 microM). Subcellular fractionation of human CEM lymphoblasts showed that extracts of mitochondria contain significant CdA phosphorylating activity (71.5 pmol/mg/min) that is not inhibited by excess of 2'-deoxycytidine (dCyd). This contrasts with the CdA phosphorylating activity found in cytosolic extracts, which is carried out by dCyd kinase and strongly inhibited by excess of dCyd. The efficient CdA phosphorylation by mitochondrial dGK is a novel finding that may have far reaching implications for the clinical use of this potent cytostatic drug.

Animals↗
PubMed1993

Clinical significance of dysplasia in gastric remnant biopsy specimens.

BACKGROUND: Dysplasia often is found in biopsy specimens from the gastric stump some 20 years after ulcer surgery. A high frequency of patients with severe dysplasia in the nonoperated stomach develop carcinoma but the clinical significance of dysplasia in the gastric stump is still confounding. METHODS: In the current study, two groups of patients were evaluated. One group of 22 patients, found at the first investigation in an endoscopic screening study with moderate dysplasia in the gastric stump, were regularly followed up to 18 years with endoscopy and biopsies. In the second part of the investigation, the authors evaluated 17 patients from the same endoscopic screening study, who at any instance during the 18 years were found to have severe dysplasia in biopsy specimens from the gastric remnant. RESULTS: In three of the 22 patients with moderate dysplasia, stump carcinoma was diagnosed 2, 2, and 6 years, respectively, after the first endoscopic examination. Severe dysplasia was found in two other patients at one occasion but later investigations only revealed moderate dysplasia. The remainder of the patients in this group had either persisting moderate dysplasia or mild dysplasia at follow-up. Seven (41%) of the 17 patients with severe dysplasia had stump carcinoma within a median time of 2 years (range, 1-11). Two other patients had surgery based on suspicion of carcinoma, but had only severe dysplasia in the surgical specimen. Finally, three men died (after 1, 2, and 17 years, respectively) of unrelated disease without suspicion of stump carcinoma and five patients were followed between 6 and 18 years without signs of malignant development. CONCLUSIONS: Patients with moderate and, especially, severe dysplasia in the gastric remnant are at high risk for gastric carcinoma. Severe dysplasia calls for endoscopic surveillance at short intervals. For patients with moderate dysplasia a close surveillance for 2 years followed by biannual evaluation appears sufficient.

Aged↗
PubMed1993

Conformational changes of the alpha 1-proteinase inhibitor affecting its cholesterol binding ability.

The effect of conformational changes of the alpha 1-proteinase inhibitor (alpha 1PI) on alpha 1PI-cholesterol complex (1:2 mol/mol) formation in vitro was studied with electrophoretic and gel chromatographic methods. Native alpha 1PI was modified by adding free thiol agents such as glutathione, cysteine HCl, or DL-homocysteine, by heating, or by cleavage with pancreatic elastase or trypsin. Conformational changes of the alpha 1PI molecule induced by these procedures were all accompanied by a loss of its ability to bind cholesterol in vitro under standard experimental conditions. The data suggest alpha 1PI-cholesterol binding to be affected by both direct and indirect modifications of the alpha 1PI-reactive center, that is situated on a mobile peptide loop.

Cholesterol↗
PubMed1993

Binding of 4',6-diamidino-2-phenylindole (DAPI) to AT regions of DNA: evidence for an allosteric conformational change.

The interaction of 4',6-diamidino-2-phenylindole (DAPI) with several double-helical poly- and oligonucleotides has been studied in solution using optical spectroscopic techniques: flow linear dichroism (LD), induced circular dichroism (CD), and fluorescence spectroscopy. In AT-rich sequences, where DAPI is preferentially bound, LD indicates that the molecule is edgewise inserted into the minor groove at an angle of approximately 45 degrees to the helix axis. This binding geometry is found for very low as well as quite high binding ratios. The concluded geometry is in agreement with that of the DAPI complex in a crystal with the Drew-Dickerson dodecamer, and the DAPI complex with this dodecamer in solution is verified to have an ICD spectrum similar to that of the complex with [poly(dA-dT)]2 at low binding ratios. The observation of two types of CD spectra characteristic for the binding of DAPI to DNA, and also for the interaction with [poly(dA-dT)]2, demonstrates that the first binding mode, despite its low apparent abundance (a few percent), is not due to a specific DNA site. The effect may be explained in terms of an allosteric binding such that when DAPI molecules bind contiguously to the AT sequence the conformation of the latter is changed. The new conformation, which according to LD appears to be stiffer than normal B-form DNA, is responsible for the second type of induced CD spectrum in the DAPI chromophore. Although the spectroscopic results indicate a change of DNA conformation, consistent with an allosteric binding model, they do not explicitly require any cooperativity, but accidental neighbors could also explain the data.

Allosteric Site↗
PubMed1993

In vitro complex formation between cholesterol and alpha 1-proteinase inhibitor.

The in vitro interaction between human alpha 1-proteinase inhibitor (alpha 1-PI) and cholesterol was studied with electrophoretic and gel chromatographic methods. The addition of cholesterol (from 1 to 20 mol/mol alpha 1-PI) at 37 degrees C resulted in retarded electrophoretic mobility of alpha 1-PI towards the anode, diminished immunoreactivity and antiproteinase activity. At a molar ratio of 2:1 (cholesterol/alpha 1-PI), antitryptic activity was reduced by 15% but antielastase activity by 50%. At this ratio the gel filtration alpha 1-PI peak appeared at 67 kDa, as compared to 52 kDa for native alpha 1-PI. No size difference was noted on SDS-PAGE. These results suggest the occurrence of noncovalent complex formation between cholesterol and alpha 1-PI in vitro.

Cholesterol↗
PubMed1993

Binding of DNA quenches tyrosine fluorescence of RecA without energy transfer to DNA bases.

The binding of single- as well as double-stranded DNA to RecA, in the presence of the cofactor analog ATP gamma S (adenosine 5'-O-(3-thiotriphosphate)), leads to about 20% quenching of the tyrosine fluorescence of the protein but to no essential change of the tryptophan fluorescence. The excitation spectrum of the fluorescent DNA analog poly(d epsilon A), complexed with RecA, shows no sign of energy transfer from the tyrosine residues of RecA to the etheno-modified adenine bases of the polynucleotide. From this observation we reject stacking interaction between tyrosine residues and DNA bases. The RecA filament may bind up to three molecules of single-stranded DNA; however, the observed fluorescence change occurs only upon the binding of the first DNA strand, indicating that the binding mode of this first strand is different from those of the others. The fluorescence change is interpreted in terms of a conformational change of the RecA protein promoted by cooperative binding to DNA. A larger quenching (40%) upon the binding of single-stranded DNA is observed in the absence of cofactor. At high salt condition, which induces ATPase activity in RecA just as DNA binding does, the tyrosine fluorescence is more pronounced than at low salt conditions, indicating that the effect induced by high salt is different from the conformational change induced by DNA binding.

Adenosine Triphosphate↗
PubMed1993

Role of tyrosine residue 264 of RecA for the binding of cofactor and DNA.

The tyrosine fluorescence of the RecA protein is quenched by about 15% upon binding of the cofactor analog adenosine 5'-O-(3-thiotriphosphate) (ATP gamma S). This quenching is not observed with a modified RecA in which the tyrosine residue at position 264 (Tyr-264) is replaced for alanine by site-directed mutagenesis, a modification which also results in a decrease of binding affinity of cofactor. This indicates that Tyr-264 is responsible for the fluorescence change and that the residue is close to or within the cofactor binding site. Upon DNA binding, a change of tyrosine fluorescence is observed both with the modified protein and with wild type RecA, indicating that DNA binding affects the environment of other tyrosine residues than Tyr-264. However, the change is significantly smaller in the modified protein, suggesting that both Tyr-264 as well as other residue(s) may be affected by the DNA binding. Changed fluorescence properties of the remaining tyrosine residues as a result of a slightly different DNA binding mode of the modified protein are also possible. Tyr-264 may be an important residue for the allosteric effect induced by the cofactor for the binding of DNA to RecA. In the recent crystal structure of RecA-ADP published by Story and Steitz (Story, R.M., and Steitz, T. A. (1992) Nature 355, 374-376), ADP is stacked with Tyr-103 and does not interact with Tyr-264. The fact that we observe no interaction of ATP gamma S with Tyr-103 (as evidenced from absence of fluorescence change) but instead with Tyr-264 may suggest an important conformational difference between the RecA complexes with, respectively, ADP and ATP.

Adenosine Triphosphate↗
PubMed1993

Binding of substrates to human deoxycytidine kinase studied with ligand-dependent quenching of enzyme intrinsic fluorescence.

Deoxycytidine kinase is a key enzyme in the salvage pathway, and its activity is required for 5'-phosphorylation of several important antiviral and cytostatic nucleoside analogues. It has recently been purified completely from human sources. Steady-state and time-resolved fluorescence of human deoxycytidine kinase was used to study its interaction with the substrates dCyd, dAdo, dUrd, dTTP, and the feedback inhibitor dCTP. Enzyme fluorescence quenching by dCTP, dCyd, dTTP, and dAdo was bimodal, and the best fits of the quenching patterns were obtained using two modified Stern-Volmer equations with two sets of quenching constants (Ksv) and accessibility values (fa) fitted independently for "low" and "high" concentration ranges of ligands. The transition between these occurred at about 20 microM dCTP, 50 microM dCyd, 30 microM dTTP, and 180 microM dAdo. Enzyme fluorescence showed unimodal quenching by dAdo and 30% reduced accessibility of the binding site in the presence of dCyd. dUrd quenching was also unimodal with Ksv = 0.0047 +/- 0.0007 microM-1 and fa = 0.75 +/- 0.05, hence in the same range as for the "high" concentration range of dAdo in the absence of dCyd, where they are 0.0025 +/- 0.0003 microM-1 and 0.73 +/- 0.03, respectively. Fluorescence quenching was used to directly determine enzyme-ligand binding and revealed bimodal binding of dCTP, dCyd, dTTP, and dAdo and unimodal binding of dUrd, and of dAdo in the presence of 0.1 microM dCyd. Transition between these two modes of binding occurred at the concentrations described above.(ABSTRACT TRUNCATED AT 250 WORDS)

Cholic Acids↗
PubMed1993

Z-->B transition in poly[d(G-m5C)2] induced by interaction with 4',6-diamidino-2-phenylindole.

The Z form of poly[d(G-m5C)2], in presence of Mg2+ ion, is found to be transformed into B form upon interaction with 4',6-diamidino-2-phenylindole (DAPI). The Z-->B transformation is complete at a mixing ratio of about 0.07 DAPI per DNA base pairs, i.e., each DAPI molecule may be related to the conversion of 6-7 base pairs. An interaction between DAPI and poly[d(G-m5C)2] in its Z form at low drug: DNA ratios is suggested from optical dichroism and time-resolved luminescence anisotropy results. The spectroscopic behaviour of DAPI indicates that the Z conformation of DNA does not provide normal binding sites for DAPI, such as groove or intercalation sites, but that the initial association may be of external nature.

Chemical Phenomena↗
PubMed1993

Catabolism of deoxycytidine in human peripheral blood mononuclear cells and its interference with the determination of in situ thymidylate synthase activity.

Resting and stimulated human peripheral blood lymphocytes and monocyte-derived macrophages were incubated with tritiated deoxycytidine labeled at the 5-position. Release of tritiated water into the medium was thereupon detected utilizing its lack of binding to active charcoal, which is an established technique to measure in situ thymidylate synthase activity. It was found that tritiated dihydrouracil, a deoxycytidine catabolite, was formed during incubation with tritiated deoxycytidine. Like water, dihydrouracil does not bind to active charcoal, and its presence in the cell medium can result in an overestimation of the in situ thymidylate synthase activity. The catabolism of dCyd was highest in macrophages where 25% of the added dCyd (0.5 microM, 0.5 nmol/million cells) had been converted to dihydrouracil after 30 min, and 90% after 12 h. The in situ thymidylate synthase activity was found to be the highest in stimulated lymphocytes. If the interference of dihydrouracil had not been considered, the activity in macrophages would have been greatly overestimated and would have appeared to be higher than that of stimulated lymphocytes.

Charcoal↗
PubMed1993

The molecular basis of alpha 1-antichymotrypsin deficiency in a heterozygote with liver and lung disease.

Alpha 1-antichymotrypsin (alpha 1-ACT) is a serine proteinase inhibitor (serpin) with cathepsin G, mast cell chymase and chymotrypsin as target enzymes. We present the case of a middle-aged man with low plasma levels of alpha 1-ACT, asthma with progression to emphysema, and chronic HCV positive liver disease with selective accumulation of alpha 1-ACT in hepatocytes. This secretory defect is analogous to that seen in Pi Z alpha 1-antitrypsin deficiency. The molecular basis of alpha 1-ACT deficiency in this patient has been characterized by direct sequencing of the alpha 1-ACT genes from the patient and his father. A C-->G transversion in exon III causing a 229Pro-->Ala substitution is proposed to cause a conformational change resulting in abnormal transport through the RER. This mutation was found in one of 20 additional tested patients with chronic obstructive lung disease, but in no control. Two additional polymorphisms of the gene have been identified in unrelated healthy individuals with normal plasma alpha 1-ACT levels. The alpha 1-ACT deficiency state may predispose to obstructive lung disease and influence the course of liver disease. Identification of a specific mutation allows identification of heterozygotes for this deficiency allowing future evaluation of its clinical significance.

Amino Acid Sequence↗
PubMed1993

Physical health and cognitive ability among married long-term-care patients and among their spouses--a comparison between home care and nursing home care.

The purpose of this study was to establish whether physical health and cognitive function in married long-term patients or in their spouses determines why some patients are cared for in home care while others reside in nursing homes. Out of 38 married couples with a sick spouse cared for in a nursing home, 23 couples were studied; out of 34 couples with a sick spouse cared for in home care, 22 patients and 25 spouses were studied. The results showed no significant differences in physical health score either between the two groups of patients, or between the two groups of spouses. Both home-care patients and nursing home patients had low cognitive function scores, but nursing home patients had significantly lower scores. A multivariate analysis showed that physical health and cognitive function explained only 20% of patients' residence. Between the two groups of spouses there was no difference in cognitive function score. The conclusion is that physical health status and cognitive function explain only to a small extent why married long-term care patients are cared for in nursing homes or in home care.

Activities of Daily Living↗
PubMed1993

HLA-DR3, DQ2 homozygosity in two patients with insulin-dependent diabetes mellitus superimposed with ulcerative colitis and primary sclerosing cholangitis.

Two unrelated young males with the unusual simultaneous presence of insulin-dependent diabetes mellitus, ulcerative colitis and primary sclerosing cholangitis are reported. Both patients manifested homozygosity for the DR3-DQw2 (DQB*0201) HLA genotypes. We believe that homozygosity for this genotype may predispose for this type of multi-organ autoimmune disease.

Adolescent↗
PubMed1993

Bone mineral density in patients with chronic hypoparathyroidism.

Photon absorptiometry was used to measure skeletal mass in the proximal femur, lumbar spine, and distal radius in 19 females with hypoparathyroidism after operation for either thyroid carcinoma or hyperparathyroidism. Healthy subjects as well as normocalcemic patients who had undergone the same surgical procedure without developing hypoparathyroidism were used as controls. Skeletal mass was measured after a mean postoperative time of 13 and 10 yr in patients operated on for thyroid carcinoma and hyperparathyroidism, respectively. Bone mass was 10-32% greater in hypoparathyroid patients than in controls. In patients with retained parathyroid function after total thyroidectomy and surgical treatment of hyperparathyroidism, bone mass did not differ from that in age-matched healthy controls. Long term T4 medication in doses that suppressed endogenous TSH production was not associated with a decreased bone mass. Reduced PTH production, vitamin D treatment, and calcium supplementation may all have contributed to the increased bone mass found in the patients with postsurgical hypoparathyroidism.

Absorptiometry, Photon↗
PubMed1993

Intravenous drug abuse--the major route of hepatitis C virus transmission among alcohol-dependent individuals?

As the prevalence of hepatitis C virus (HCV) antibodies has been reported to be high among alcohol-dependent individuals, we screened prospectively 310 consecutive non-selected alcoholic outpatients for HCV and possible routes of transmission. Using a second-generation enzyme-linked immunosorbent assay test and retesting all positive sera with a second-generation recombinant immunoblot assay, we found the prevalence of anti-HCV to be 14.5% (45 of 310). Of the 45 anti-HCV-positive individuals, 39 (88.7%) had a history of intravenous drug abuse, 2 had received blood transfusions, and only 4 lacked an identifiable source of infection. The magnitude of alcohol consumption, number of hospital admissions, duration of alcohol dependence, or presence of tattooing could not be shown to be factors of importance for the transmission of HCV infection. Our results suggest that a history of intravenous drug abuse is a common phenomenon and the predominant route of HCV transmission among alcoholics. True community-acquired infection would appear to be rare.

Adult↗
PubMed1993

Patterns of abuse of the elderly in their own homes as reported by district nurses.

This study aimed at describing patterns of abuse of elderly persons living in their homes as experienced by district nurses in a county of Sweden. 12% of the district nurses (n = 153) reported 30 cases. Those abused were 78.7 years old (mean) and half of them had disturbed memory and mental state and were mostly isolated. The abuser was a relative of the abused person and 64.2 years old (mean). Psychological abuse was the most frequently reported kind of abuse. Along with the abuse the abusers' behaviour was commonly experienced as unpleasant and aggressive and/or combined with family conflicts. The results indicated that abuse is very much a family affair. To guide district nurses in a family-oriented approach is justified by the results. It also seems important further to investigate the pattern of how the different types of abuse occur.

Aged↗