Biomedical subjects

G Magnusson

Publications and source records attributed to G Magnusson.

At least 37 records · Page 2Linked to original sources

PubMed1999

The occurrence of congenital cataract in western Sweden.

PURPOSE: To estimate the occurrence of congenital cataract in a Nordic country. METHODS: In 1980, we constructed a database in the Department of Ophthalmology, Göteborg University, containing basic data from all cases in western Sweden diagnosed with congenital cataract. By collecting and processing these data from 1980 onwards, we hoped to improve the management of congenital cataract treatment and to optimize the outcome of the treatment. RESULTS: In this study, the incidence of congenital cataract in the four western counties of Sweden was evaluated. The occurrence rate of all cases with congenital cataract during the study period was 36 cases per 100,000. The occurrence rate for dense bilateral and all unilateral cases were both 14 per 10,0000 each. CONCLUSION: There were no time-related changes in incidence of congenital cataract from 1980 until today, although there was a large variation in the yearly incidence.

Cataract↗

PubMed1999

Inheritance of strabismus and the gain of using heredity to determine populations at risk of developing strabismus.

PURPOSE: In the Nordic countries 2 to 4% of the population squint or have been squinting. Since strabismus is one of the major causes of amblyopia early detection and treatment is important for preventing this development. For centuries it has been recognized that strabismus is hereditary. Identifying individuals with a family history of squinting could give access to a risk population for a selective screening. METHODS AND RESULTS: 1,571 children were selected for this study. All children that took part in a voluntary eye examination at one year of age (born 1978-1983) in the city of Vasteras, Sweden and that had a family history of strabismus were selected together with controls. The study was a 6-year follow-up from 1 to 7 years of age. Parental knowledge of squint among relatives and measured high hyperopia (>3.0 D) present at 1 year of age were each and in combination evaluated as a risk indicator for development of strabismus between 1 to 7 years of age. CONCLUSION: The study indicates that a family history of squint in combination with measured high hyperopia can be used in a selective screening to identify a population with an increased risk of 4 to 6 times for developing strabismus. Among the children with parental knowledge of squint among several relatives of both the parents, those with high hyperopia developed strabismus in almost every second case while this was the case in only approximately 10% of those with low hyperopia. Finally, heredity is an important risk indicator that can be used for selective screening purpose. Its potential as a risk indicator is substantially increased when combined with a high hyperopia.

Child↗

PubMed1998

DNA binding of polyomavirus large T-antigen: kinetics of interactions with different types of binding sites.

Polyomavirus large T-antigen binds to GRGGC sites in double-stranded viral DNA, regulating transcription and replication. Using surface plasmon resonance to record interactions of large T-antigen with different types of binding sites, we found that the configuration of recognition motifs influenced both the association and dissociation rates. Particularly, the complex formed at the origin of DNA replication was labile. A comparison of the interactions between large T-antigen and binding sites with one, two and four GRGGC motifs in tandem showed a strong preference for dimer binding, without detectable co-operativity between dimers. Sodium chloride stabilised the complexes, whereas the dissociation increased rapidly by increasing pH above 7.0.

Antigens, Viral, Tumor↗

PubMed1998

Characterization of a rotavirus rearranged gene 11 by gene reassortment.

The effect of replacement of gene 11 of rotavirus SA-11 by a gene carrying a head to tail duplication obtained from a swine rotavirus strain was studied. The swine rotavirus strain with a duplicated gene (CC86) exhibits both a phenotype that allows to overgrow other viral strains when coinfected and an increased plaque size when plated in both CV-1 and MA-104 monkey kidney cells. Using reassortment methods the duplicated gene of the swine rotavirus was introduced into the SA-11 virus, replacing the regular gene 11. The reassorted strain was characterized to find out the origin of each of the other viral gene segments. Based on electrophoretic mobilities segments 1, 2, 3, 5, 7, 8 and 10 were identified as of SA-11. The SA-11 origin of the segments 4, 6 and 9 was confirmed by neutralization with polyclonal and monoclonal antibodies and by ELISA. The results suggest that the new reassortant virus was a monoreassortant carrying SA-11 genes except the duplicated gene originated from the swine virus CC86. The ability to in vivo replicate and to synthesize viral proteins was identical in the reassorted virus and the parental strains. Sequence analysis indicates that the new phenotype does not originate in the duplication of gene 11 but possibly from mutations in the coding region of NSP5 gene that may result in different phosphorylation patterns of the protein.

Amino Acid Sequence↗

PubMed1998

Synthesis of some amino and carboxy analogs of galabiose; evaluation as inhibitors of the pilus protein PapGJ96 from Escherichia coli.

The 2'-amino-2'-deoxy, 6-amino-6-deoxy, and 6-carboxy analogs of the reference inhibitors 2-(trimethylsilyl)ethyl (alpha-D-galactopyranosyl)-(1-->4)-ss-D-galactopyranoside were synthesized and evaluated as inhibitors of the binding of the Escherichia coli-derived pilus protein PapGj96, using an ELISA assay. The inhibitory efficiencies (Krel; relative to the reference inhibitor) were: 157,13, and < 8, respectively. The results support the previously proposed combining site model, where the protein carries a negatively charged amino acid residue near HO-2' and HO-6 of the galabio-side.

Adhesins, Escherichia coli↗

PubMed1998

Synthesis of some divalent O- and S-glycosides of galabiose and globotriose.

Derivatives of galabiose (alpha-D-Galp-(1-->4)-D-Galp) and globotriose (a-D-Galp-(1-->4)-beta-D-Galp-(1-->4)-D-Glcp) were coupled to various 1,2- and 1,3-dihydroxymethyl- and dimercapto-methylbenzenes to give the corresponding divalent glycosides, potentially useful as inhibitors of bacterial adhesion.

Carbohydrate Sequence↗

PubMed1998

Analysis of rotavirus nonstructural protein NSP5 phosphorylation.

The rotavirus nonstructural phosphoprotein NSP5 is encoded by a gene in RNA segment 11. Immunofluorescence analysis of fixed cells showed that NSP5 polypeptides remained confined to viroplasms even at a late stage when provirions migrated from these structures. When NSP5 was expressed in COS-7 cells in the absence of other viral proteins, it was uniformly distributed in the cytoplasm. Under these conditions, the 26-kDa polypeptide predominated. In the presence of the protein phosphatase inhibitor okadaic acid, the highly phosphorylated 28- and 32- to 35-kDa polypeptides were formed. Also, the fully phosphorylated protein had a homogeneous cytoplasmic distribution in transfected cells. In rotavirus SA11-infected cells, NSP5 synthesis was detectable at 2 h postinfection. However, the newly formed 26-kDa NSP5 was not converted to the 28- to 35-kDa forms until approximately 2 h later. Also, the protein kinase activity of isolated NSP5 was not detectable until the 28- and 30- to 35-kDa NSP5 forms had been formed. NSP5 immunoprecipitated from extracts of transfected COS-7 cells was active in autophosphorylation in vitro, demonstrating that other viral proteins were not required for this function. Treatment of NSP5-expressing cells with staurosporine, a broad-range protein kinase inhibitor, had only a limited negative effect on the phosphorylation of the viral polypeptide. Staurosporine did not inhibit autophosphorylation of NSP5 in vitro. Together, the data support the idea that NSP5 has an autophosphorylation activity that is positively regulated by addition of phosphate residues at some positions.

Animals↗

PubMed1997

Peak skeletal muscle perfusion is maintained in patients with chronic heart failure when only a small muscle mass is exercised.

OBJECTIVES: The issue to be resolved was whether peripheral leg blood flow in patients with chronic heart failure (CHF) is reduced by low local flow capacity or as a function of the amount of muscle mass activated during exercise. METHODS AND RESULTS: In ten CHF patients (ejection fraction 26 (9)%), and 12 healthy controls central and peripheral circulatory responses were assessed during dynamic one- and two-legged knee extensor work. The patients reached a peak perfusion of 234 (16) ml 100 g-1 min-1 in the one-legged mode, which was similar to the controls (244 (11) ml 100 g-1 min-1). At peak two-legged work muscle perfusion was reduced in the patients by 24% (P < 0.05). In contrast the controls maintained their peak muscle perfusion. The mass of the quadriceps femoris muscle and peak leg blood flow correlated closely for both groups at peak one-legged work (r = 0.85, P < 0.001). Peak oxygen uptake in the active limb during one-legged exercise was similar for patients and controls (0.52 (0.06) vs. 0.63 (0.06) l min-1), but it was 38% lower (P < 0.05) in patients than controls during exhaustive two-legged exercise. Arterial systemic oxygen delivery (cardiac output x arterial oxygen content), at peak exercise was highly correlated with peak one- and two-legged workload for both groups, explaining 70% of the difference in peak workload attained (P < 0.001). At peak two-legged exercise non-exercising tissues of the body in the male CHF patients with the largest limb muscle mass, received a blood flow of only 1.2 (0.7) 1 min-1. Mean arterial blood pressure at peak work in both test conditions was significantly lower for the patients than the controls. A higher sympathetic nerve activity in the patients, as evaluated by arterial noradrenaline concentration (NA) and leg NA spillover, contributed to maintain the perfusion pressure. CONCLUSIONS: Patients with moderate CHF can reach a peak skeletal muscle perfusion and a leg oxygen uptake comparable to that of healthy individuals when a sufficiently small muscle mass is activated. Exercise involving a larger muscle mass, for the patients in this study about 4 kg, markedly reduces peak leg blood flow, perfusion and oxygen uptake as well as blood flow to non-exercising organs and tissues.

Cardiac Output↗

PubMed1997

Plasma and tissue levels of lipids, fatty acids and plasma carnitine in neonates receiving a new fat emulsion.

This study was undertaken to compare Intralipid with a new fat emulsion containing gamma-linolenic acid and carnitine, named Pediatric Fat Emulsion 4501, in neonates with regard to lipid and carnitine metabolism over a short period of total parenteral nutrition. There were 10 neonates in each group and they tolerated the total parenteral nutrition well. In spite of the gamma-linolenic acid supplementation in the new emulsion, arachidonic acid decreased significantly in plasma lipid esters and adipose tissue in both groups after 5 d of treatment. Also, there was a decrease in plasma docosahexaenoic acid which was more pronounced in the treatment group. The relative percentage values of linoleic and linolenic acids in adipose tissue were increased, indicating that newborns have a rapid accretion of fatty acids. Plasma-triglycerides were effectively cleared during the periods without fat infusion. In the group that received Pediatric Fat Emulsion 4501 the means of both free and total plasma carnitine concentrations increased significantly, whereas they tended to decrease in the Intralipid group.

Adipose Tissue↗

PubMed1997

Serine protein kinase activity associated with rotavirus phosphoprotein NSP5.

The rotavirus nonstructural protein NSP5, a product of the smallest genomic RNA segment, is a phosphoprotein containing O-linked N-acetylglucosamine. We investigated the phosphorylation of NSP5 in monkey MA104 cells infected with simian rotavirus SA11. Immunoprecipitated NSP5 was analyzed with respect to phosphorylation and protein kinase activity. After metabolic labeling of NSP5 with 32Pi, only serine residues were phosphorylated. Separation of tryptic peptides revealed four to six strongly labeled products and several weakly labeled products. Phosphorylation at multiple sites was also shown by two-dimensional polyacrylamide gel electrophoresis (PAGE), where several isoforms of NSP5 with different pIs were identified. Analysis by PAGE of protein reacting with an NSP5-specific antiserum showed major forms at 26 to 28 and 35 kDa. Moreover, there were polypeptides migrating between 28 and 35 kDa. Treatment of the immunoprecipitated material with protein phosphatase 2A shifted the mobilities of the 28- to 35-kDa polypeptides to the 26-kDa position, suggesting that the slower electrophoretic mobility was caused by phosphorylation. Radioactive labeling showed that the 26-kDa form contained additional phosphate groups that were not removed by protein phosphatase 2A. The immunoprecipitated NSP5 possessed protein kinase activity. Incubation with [gamma-32P]ATP resulted in 32P labeling of 28- to 35-kDa NSP5. The distribution of 32P radioactivity between the components of the complex was similar to the phosphorylation in vivo. Assays of the protein kinase activity of a glutathione S-transferase-NSP5 fusion polypeptide expressed in Escherichia coli demonstrated autophosphorylation, suggesting that NSP5 was the active component in the material isolated from infected cells.

Animals↗

PubMed1997

Altered susceptibility to tumor necrosis factor alpha-induced apoptosis of mouse cells expressing polyomavirus middle and small T antigens.

Infection with some virus types induces susceptibility to the cytotoxic effect of tumor necrosis factor alpha (TNF-alpha). To investigate whether expression of polyomavirus proteins has this effect on cells, the TNF-alpha sensitivity of C127 and L929 mouse cells transfected with viral DNA was analyzed. Expression of all three polyomavirus early proteins, the tumor (T) antigens, had no apparent effect. In contrast, middle T antigen by itself induced hypersensitivity to TNF-alpha. This effect was reversed by retransfection of the cells with DNA encoding small T antigen. Expression of this polypeptide also decreased the sensitivity of bovine papillomavirus type 1-transformed cells to TNF-alpha, showing that the protective function of the polyomavirus small T antigen was not strictly linked to a middle-T-antigen-induced event. Mouse and human TNF-alpha had the same effect on normal and transformed mouse cells, suggesting that this effect was mediated by TNF receptor 1. Consistent with this conclusion, all cell clones used in the experiments expressed TNF receptor 1 at similar levels, while we failed to detect TNF receptor 2. The amount of receptor on the cells was not influenced by binding of the ligand. Addition of TNF-alpha at cytotoxic concentrations to cells expressing middle T antigen by itself resulted in significant fragmentation of chromosomal DNA after only a few hours, indicating induction of apoptosis. Addition of the cytokine to these cells also leads to release of arachidonic acid, showing that phospholipase A2 was activated. However, production of arachidonic acid did not appear to significantly precede loss of cell viability.

Animals↗

PubMed1996

Conversion of p-methoxyphenyl glycosides into the corresponding glycosyl chlorides and bromides, and into thiophenyl glycosides.

p-Methoxyphenyl (pMP) beta-D-glycopyranosides (Glc, Gal, GlcNPhth, GalNPhth, GlcNTroc, Gal beta 4Glc, Gal alpha 4Gal) were prepared from the corresponding 1-O-acetyl sugars in 79-90% yield, using boron trifluoride etherate as promoter. Treatment of the pMP glycosides with acyl chlorides or bromides in the presence of various Lewis acids gave the corresponding glycosyl chlorides and bromides in 81-98% yield. Treatment of the acyl-protected pMP glycosides with thiophenol and boron trifluoride etherate gave the corresponding thioglycosides in 80-100% yield and high (> 20:1) beta/alpha selectivity. The stability of pMP glycosides was investigated against a series of reagents.

Anisoles↗

PubMed1996

Genetic stability of a porcine rotavirus RNA segment during repeated plaque isolation.

The porcine group A rotavirus CC86 was characterized to explore its utility as a tool for mutation analysis. It has a semiduplication of the gene 11 RNA segment. Nucleotide sequence determination of cDNA confirmed that the NSP5 coding sequence and the conserved nontranslated termini of the RNA segment were retained. A comparison of the NSP5 genes of CC86 and CN86 that were isolated from the same fecal specimen showed eight base pair changes, suggesting that CN86 was not the immediate progenitor of CC86. Synthesis of NSP5 in monkey MA104 cells infected with CC86, CN86, or simian rotavirus SA11 was compared by one- and two-dimensional polyacrylamide gel electrophoresis. NSP5 from all three viruses had similar posttranslational modifications, and no difference in the expression levels was observed. To experimentally address the genetic stability of CC86 segment 11, the virus was passaged by serial plaque to plaque transfer. The repeated genetic bottlenecking led to a gradual loss of fitness. This effect is not observed when virus is passaged by the standard method of moderate dilution. Nucleotide sequence analysis of cDNA clones isolated from viral segment 11 RNA of virus from plaque-to-plaque passage numbers 0, 1, 4, and 8 showed occasional base substitutions, mostly in the NSP5 coding sequence. Two mutations, leading to His-to-Arg and Lys-to-Arg replacements, respectively, in NSP5 were established in the virus population. Forward and reverse base pair changes (A-U<-->G-C) at the two sites appeared to be concerted and take place at a very high frequency, suggesting that a mechanism equivalent to RNA editing might operate. The overall mutation rate of segment 11 was much lower, having a calculated maximal value of 5 x 10(-5) per replicated base.

Animals↗

PubMed1996

Reasons for not accepting living kidney donors.

Organs were donated by a small number of relatives (54/146=37%), genetically related or familial, who volunteered to give a kidney to a relative or spouse at our institution in 1991-1994. The most common reason for not accepting them was an immunological incompatibility (30 cases), followed by a diagnosis of hypertension and/or renal disease (24 cases). Other medical contraindications-including heart/lung disease, obesity, latent diabetes, and hepatic disease-were found in 14 potential donors. One woman (22 years of age) was judged too young for donation. Five ESRD patients died before the investigation of the donor had been completed. Eighteen potential donors changed their minds and decided not to donate a kidney. Interestingly, there was a high percentage of denial of spouses due to positive crossmatches.

Adult↗

PubMed1996

Glycosylation with N-Troc-protected glycosyl donors.

N-Troc-protected (Troc = 2,2,2-trichloroethoxycarbonyl) glucosamine and galactosamine glycosyl donors (1-O-acetyl sugar, bromo sugar, and thioglycoside) were compared with the corresponding N-Phth-protected derivatives in glycosylations of 2-(trimethylsilyl)ethanol, 2-bromoethanol, methyl 3-mercaptopropionate, N-Fmoc-protected serine, and 2-(trimethylsilyl)ethyl 6-O-benzyl-2-deoxy-2-phthalimido-beta-D-glucopyranoside. The N-Troc-protected donors gave pure beta-glycosides in somewhat higher yields than the N-Phth-protected counterparts. The N-Troc protecting group can be removed by reduction with zinc, which allows selective N-deprotection in oligosaccharides containing both N-Troc and N-Phth groups.

Carbohydrate Sequence↗

PubMed1996

Immunization with glycosylated Kb-binding peptides generates carbohydrate-specific, unrestricted cytotoxic T cells.

Cytotoxic T cells (CTL) recognize target proteins as short peptides presented by major histocompatibility complex (MHC) class I restriction elements. However, there is also evidence for peptide-independent T cell receptor (TCR) recognition of target proteins and non-protein structures. How such T cell responses are generated is presently unclear. We generated carbohydrate (CHO)-specific, MHC-unrestricted CTL responses by coupling di- and trisaccharides to Kb- or Db-binding peptides for direct immunization in mice. Four peptides and three CHO have been analyzed with the CHO either in terminal or central position on the carrier peptide. With two of these glycopeptides, with galabiose (Gal alpha 1-4Gal; Gal2) bound to a homocysteine (via an ethylene spacer arm) in position 4 or 6 in a vesicular stomatitis virus nucleoprotein-derived peptide (RGYVYQGL binding to Kb), CTL were generated which preferentially killed target cells treated with glycopeptide compared to those treated with the core peptide. Polyclonal CTL were also found to kill target cells expressing the same Gal2 epitope in a glycolipid. By fractionation of CTL, preliminary data indicate that glycopeptide-specific Kb-restricted CTL and unrestricted CHO-specific CTL belong to different T cell populations with regard to TCR expression. The results demonstrate that hapten-specific unrestricted CTL responses can be generated with MHC class I-binding carrier peptides. Different models that might explain the generation of such responses are discussed.

Amino Acid Sequence↗

PubMed1996

PapG adhesin from E. coli J96 recognizes the same saccharide epitope when present on whole bacteria and as isolated protein.

Purified PapG adhesin from the genetically well-defined uropathogenic Escherichia coli strain J96, as well as whole bacteria, were bound to microtiter plates that carried covalently bound globotetraose and galabiose. The binding was inhibited by soluble saccharide derivatives corresponding to the glycolipids, including all di-, tri-, tetra-, and pentasaccharide fragments of the Forssman antigen and all monodeoxy analogues of galabiose. Analysis of the inhibition pattern showed no significant difference between purified adhesin and whole bacteria. The glucose unit at the reducing end of the natural saccharides was detrimental to PapG binding since deletion of the glucose unit increased the inhibitory power 10-20 fold. The five hydroxyl groups HO-6, -2', -3', -4', -6' of the galabiose unit were shown to be important for PapG binding, presumably via intermolecular hydrogen bonds.

Adhesins, Escherichia coli↗

PubMed1996

Two distinct binding sites for globotriaosyl ceramide on verotoxins: identification by molecular modelling and confirmation using deoxy analogues and a new glycolipid receptor for all verotoxins.

BACKGROUND: The Escherichia coli verotoxins (VTs) can initiate human vascular disease via the specific recognition of globotriaosyl-ceramide (Gb3) on target endothelial cells. To explore the structural basis for receptor recognition by different VTs we used molecular modelling based on the crystal structure of VT1, mutational data and binding data for deoxy galabiosyl receptors. RESULTS: We propose a model for the verotoxin 'cleft-site complex' with Gb3. Energy minimizations of Gb3 within the 'cleft site' of verotoxins VT1, VT2, VT2c and VT2e resulted in stable complexes with hydrogen-bonding systems that were in agreement with binding data obtained for mono-deoxy analogues of Gb3. N-deacetylated globoside (aminoGb4), which was found to be a new, efficient receptor for all verotoxins, can be favourably accommodated in the cleft site of the VTs by formation of a salt bridge between the galactosamine and a cluster of aspartates in the site. The model is further extended to explain the binding of globoside by VT2e. Docking data support the possibility of an additional binding site for Gb3 on VT1. CONCLUSIONS: The proposed models for the complexes of verotoxins with their globoglycolipid receptors are consistent with receptor analogue binding data and explain previously published mutational studies. The results provide a first approach to the design of specific inhibitors of VT-receptor binding.

Bacterial Toxins↗