Search PubMed⌕ Search

Biomedical subjects

K Kristiansen

Publications and source records attributed to K Kristiansen.

At least 91 records · Page 5Linked to original sources
PubMed1991

Gene synthesis, expression in Escherichia coli, purification and characterization of the recombinant bovine acyl-CoA-binding protein.

A synthetic gene encoding the 86 amino acid residues of mature acyl-CoA-binding protein (ACBP), and the initiating methionine was constructed. The synthetic gene was assembled from eight partially overlapping oligonucleotides. Codon usage and nucleotides surrounding the ATG translation-initiation codon were chosen to allow efficient expression in Escherichia coli as well as in yeast. The synthetic gene was inserted into the expression vector pKK223-3 and expressed in E. coli. In maximally induced cultures, recombinant ACBP constitutes 12-15% of total cellular protein. A fraction highly enriched for recombinant ACBP was obtained by extracting induced E. coli cells with 1 M-acetic acid. Recombinant ACBP was purified to homogeneity by successive use of gel-filtration chromatography, ion-exchange chromatography and reverse-phase h.p.l.c. Recombinant ACBP differed from native ACBP by lacking the N-terminal acetyl group. The acyl-CoA-binding characteristics of recombinant ACBP did not differ from those of native ACBP, and the two proteins showed the same ability to induce medium-chain acyl-CoA synthesis by goat mammary-gland fatty acid synthetase. It was concluded that the N-terminal acetyl group is not important for acyl-CoA binding.

Acyl Coenzyme A↗
PubMed1991

Structure and evolution of the Tetrahymena thermophila gene encoding ribosomal protein L21.

The single-copy gene encoding ribosomal protein (r-protein) L21 in the macronucleus of the ciliate Tetrahymena thermophila was cloned and characterized. Sequencing of the L21 gene and a corresponding cDNA clone showed the gene to contain three introns, all located in the 3' half of the coding region. Primer extension and nuclease protection analyses revealed five transcription start points (tsp) 56-73 nucleotides upstream from the start codon. The uppermost tsp mapped to the first T in a sequence, TATAA, often found at tsp in T. thermophila. A comparison of amino acid sequences of r-proteins revealed that T. thermophila L21 belongs to a family of r-proteins that have been conserved in eubacteria, archaebacteria and eukaryotes. On the basis of structural and functional considerations, we suggest that the eukaryotic, like the prokaryotic, members of this protein family interact with the 5S RNA complex in ribosomes.

Amino Acid Sequence↗
PubMed1991

Lymphocytic 2',5'-oligoadenylate synthetase is insensitive to dsRNA and interferon stimulation in autoimmune BB rats.

The interferon (IFN)-dependent 2',5'-oligoadenylate synthetase (2-5A synthetase), which produces 2',5'-oligoadenylates from ATP, was analyzed in homogenates of isolated peripheral blood lymphocytes (PBL) from BB and Sprague-Dawley rats, man, sheep, and beagle dog. In all the examined species, the 2-5A synthetase was expressed constitutively and showed sensitivity differences to poly(I:C) (synthetic dsRNA). The 2-5A synthetase activity in the absence of poly(I:C) was high in the BB and Sprague-Dawley rat where only 2-5A dimers were synthesized. With the notable exception of PBL homogenates from BB rats, increasing poly(I:C) concentrations resulted in an increased 2-5A synthetase activity leading to the production of higher 2-5A oligomers, predominantly the octamer. Diabetes-resistant, diabetes-prone, and diabetic BB rats were indistinguishable in that their 2-5A synthetase was insensitive to poly(I:C). Preincubation of PBL from BB and Sprague-Dawley rats with up to 1,000 U/ml rat IFN elicited a moderate increase of 60% in the activity level of 2-5A synthetase. In contrast, preincubation of human PBL with human IFN-alpha led as expected to a 300% increase in 2-5A activity. Thus, the BB rat was markedly different from the other species in producing only the biologically inactive 2-5A dimers and in having a high basal 2-5A synthetase activity, that was unaffected by poly(I:C). We believe that these factors per se or together may render the BB rat more susceptible to virus attacks and/or may create a background that will facilitate the development of autoimmune processes.

2',5'-Oligoadenylate Synthetase↗
PubMed1991

Comparative analysis of autosomes in karyotypes from pig and rabbit using RBG-banding and in situ hybridization.

The chromosomal location of the porcine gene for glucose phosphate isomerase (GPI) was previously mapped to 6p 12----6q21 in the pig karyotype. The replication patterns and morphology of this chromosome are very similar to those of chromosome 14 in the rabbit karyotype. With combined in situ hybridization and RBG-band induction it was demonstrated that the porcine GPI-probe hybridized most frequently to 14p11----14q12 in the rabbit karyotype, indicating a close relationship between morphology, replication pattern and gene location.

Animals↗
PubMed1990

Vilhelm Magnus--pioneer neurosurgeon.

In parallel with but completely independent from Harvey Cushing, Norway had its own giant in the establishment of the special field of neurological surgery. Vilhelm Magnus (1871-1929), born in the United States in Fillmore County, Minnesota, was Norway's pioneering neurosurgeon. Following graduation in Oslo, he started his clinical training in neurology and became an early member of the small group of neurologists of the time who were dissatisfied with the therapeutic nihilism generally accepted in relation to diseases of the nervous system. After working with Victor Horsley, whom he held in high esteem. Magnus devoted himself to surgically treatable lesions in the nervous system. During a quarter of a century he single-handedly established the special field of neurological surgery in Norway. Magnus was a far-seeing and brilliant surgeon with a broad intellectual mind, a startling diligence, and wide research activities. He published his first scientific paper in 1899 and his total contribution to the literature amounted to 70 papers. In 1901 he was able to demonstrate the importance of the corpus luteum in the first 3 weeks of pregnancy. As early as 1903 Magnus manifested his interest in the surgical treatment of brain tumors. In 1926 his surgical material comprised 216 patients, with an 8% operative mortality rate among 161 cases of supratentorial tumor versus 17% for 55 cases of infratentorial tumors, including 14 cases of acoustic tumor. Vilhelm Magnus, who visited Harvey Cushing in 1928, has hitherto not been given the attention he merits.

Female↗
PubMed1987

Unusual ciliate-specific codons in Tetrahymena mRNAs are translated correctly in a rabbit reticulocyte lysate supplemented with a subcellular fraction from Tetrahymena.

The codon usage of Tetrahymena thermophila and other ciliates deviates from the 'universal genetic code' in that UAA and probably UAG are not translational termination signals but code for glutamine. Therefore, translation in vitro of mRNA from Tetrahymena in a reticulocyte lysate is prematurely terminated if a UAA or UAG triplet is present in the reading frame of the mRNA. We show that the addition of a subcellular fraction from Tetrahymena thermophila enables a rabbit reticulocyte lysate to translate Tetrahymena mRNAs into full-sized proteins. The activity of the subcellular fraction is shown to depend on the combined function of a protein component(s) and a tRNA(s). The subcellular fraction is easily prepared and its usefulness for the identification of isolated mRNAs from Tetrahymena by their translation products in vitro is demonstrated.

Animals↗
PubMed1987

Toxins, putative cell adhesins and fibronectin binding properties of Salmonella dublin.

Fifty Salmonella dublin strains isolated from cattle and human diarrhoeal cases were assayed for toxin production, haemagglutination, cell-surface hydrophobicity and fibronectin-binding properties. Most strains (65% of tested) produced cytotonic toxins and cytotoxic factors when tested on Chinese hamster ovary (CHO) cells and rabbit skin test. However, only three strains produced a skin-permeability factor as determined in pig skin intra-dermal tests. None of the strains were positive in pig intestinal loop tests. Six of the 32 strains tested for 125I-fibronectin and its 125I-29 kDa N-terminal domain binding showed 10-17% and 6-10% binding, respectively. Most of the strains expressed mannose-sensitive haemagglutination (MSHA) (76%) and high cell-surface hydrophobicity (74%) when grown at 37 degrees C. At 20 degrees C the expression of MSHA and especially the expression of high cell-surface hydrophobicity were reduced. Twelve strains grown at 37 degrees C did not haemagglutinate erythrocytes from five animal species used in this study, while six of these strains expressed high cell-surface hydrophobicity. Salmonella dublin strains isolated in Denmark appeared to express a higher frequency of fimbriae type 1 (MSHA) and a lower frequency of high cell-surface hydrophobicity than the strains from external sources.

Animals↗
PubMed1987

When Nordic neurosurgery was still in its infancy.

Olof af Acrel, the father of Swedish Surgery, operated in 1768 upon a young nobleman who had experienced an increasing swelling on the skull, due to a tumour which also turned out to be growing deep into the brain parenchyma. The patient survived the operation for 3 days. Edvard Bull in 1877, after diagnosing a ruptured internal carotid artery aneurysm in a young female who temporarily recovered after her first hemorrhage, emphasised that the risk of a second, fatal haemorrhage--which in fact occurred--was immediate. He predicted that carotid ligation might be a way to reduce the risk of repeated haemorrhage from such aneurysms. Virtually unknown to modern neurosurgeons are many remarkable Nordic pioneers who, in the 1800's and early 1900's, rendered major contributions to the birth of modern neurological surgery. Thus early neurosurgical operations were performed by Carl Daniel von Haartman in Finland and by Christopher Withusen and Gundelach Møller in Denmark. von Haartman and Withusen had both visited Sir Astley Cooper in London in 1816. Vilhelm Magnus of Oslo was a neurosurgical giant, who had been trained by Victor Horsley during visits to London in 1903 and 1904. Magnus performed his first two-stage operation for a tumour located deep in the left cerebral hemisphere in 1903. By 1921, he had operated upon 112 cases of intracranial tumour with an 8.1% surgical mortality. His results were certainly fully comparable with those of his contemporary American pioneer--Harvey Cushing. Vilhelm Magnus, who worked alone under primitive conditions in small private hospitals, published altogether 70 scientific papers. In 1925 his series comprised 189 patients operated upon for brain tumours with 7.7% surgical mortality in supratentorial, and 17.8% mortality in infratentorial tumours. Magnus was congratulated on his brilliant achievements by a Swedish colleague 20 years his junior, Herbert Olivecrona, the man who was to carry on his pioneering work in Sweden.

History, 18th Century↗
PubMed1986

An intron in a ribosomal protein gene from Tetrahymena.

We have cloned and sequenced a single copy gene encoding a ribosomal protein from the ciliate Tetrahymena thermophila. The gene product was identified as ribosomal protein S25 by comparison of the migration in two-dimensional polyacrylamide gels of the protein synthesized by translation in vitro of hybrid-selected mRNA and authentic ribosomal proteins. The proteins show strong homology to ribosomal protein S12 from Escherichia coli. The coding region of the gene is interrupted by a 979-bp intron 68 bp downstream of the translation start. This is the first intron in a protein encoding gene of a ciliate to be described at the nucleotide sequence level. The intron obeys the GT/AG rule for splice junctions of nuclear mRNA introns from higher eukaryotes but lacks the pyrimidine stretch usually found in the immediate vicinity of the 3' splice junction. The structure of the intron and the fact that it is found together with the well described self-splicing rRNA intron is discussed in relation to the evolution of RNA splicing.

Journal Article↗
PubMed1986

The increases in the rates of synthesis of ribosomal proteins and ribosomal RNA during refeeding of starved Tetrahymena cells are not dependent on DNA replication.

We have analysed the effects of an inhibition of DNA replication by hydroxyurea on the synthesis of ribosomal proteins (r-proteins) and ribosomal RNA (rRNA) in Tetrahymena cells resuming growth after long-term starvation. The coordinate regulation of the synthesis of individual r-proteins and their increased rate of synthesis during refeeding are not impaired by inhibition of DNA replication. Moreover, the presence of hydroxyurea does not prevent an increase in the rate of synthesis of rRNA around 70-80 min after refeeding. Previously, this increase was claimed to be gene dose-dependent. Up to 180 min after refeeding, the synthesis of r-proteins appears to be closely coupled with that of rRNA and proceed in stoichiometric balance, irrespective of whether hydroxyurea is present or not. After 180 min of refeeding in the presence of hydroxyurea, this stoichiometric balance breaks down, and the rate of synthesis of r-proteins clearly exceeds that of the rRNA synthesis.

Animals↗
PubMed1985

Combined modality treatment of operated astrocytomas grade 3 and 4. A prospective and randomized study of misonidazole and radiotherapy with two different radiation schedules and subsequent CCNU chemotherapy. Stage II of a prospective multicenter trial of the Scandinavian Glioblastoma Study Group.

A prospective and randomized trial has been performed in order to evaluate combined modality therapy in patients with astrocytomas grade 3 and 4. Follow-up information is available on 244 patients. One half of the series received radiation therapy twice a week (40.00 Gy/5 weeks), the other half five times a week (50.00 Gy/5 weeks). Misonidazole 1.2 g/m2 was given orally to one half of the patients in the first radiation treatment group 3 1/2 to 4 hours before the treatment. The other half received placebo. The second radiation treatment group was also divided in two halves, one receiving 0.48 g/m2 misonidazole and the other placebo 3 1/2 to 4 hours before radiation. The randomization also included a subdivision of the material into eight groups of which four were given CCNU and four no chemotherapy, beginning 3 months after operation. The dose of CCNU was 120 mg/m2 body surface every 6 weeks. All eight treatment groups showed practically identical periods of median survival, and no statistically significant differences were observed with regard to performance status, side effects, or complications. Another dosage and timing of misonidazole administration in relation to the irradiation schedule, and a consideration of effects of concomitant drugs like dexamethasone and phenytoin are discussed.

Actuarial Analysis↗
PubMed1984

Regulation of ribosome synthesis in Tetrahymena pyriformis. 1. Coordination of synthesis of ribosomal proteins and ribosomal RNA during nutritional shift-down.

When exponentially growing cells of Tetrahymena pyriformis are transferred to a non-nutrient medium the loss of whole cell RNA, 90% of which is ribosomal RNA, exhibits biphasic kinetics, whereas whole cell protein is lost at a constant rate. The ratio RNA/protein declines during the first 5 h of starvation and then remains constant during the subsequent period of starvation. The synthesis of the majority of the ribosomal proteins is coordinately regulated during a nutritional shift-down. Exponentially growing cells devote 17% of their capacity for protein synthesis to the production of ribosomal proteins. Upon starvation this proportion is rapidly reduced 3.5-fold. In long-time-starved cells the absolute rate of ribosomal protein synthesis is only about 4.5% of that of exponentially growing cells. The synthesis of ribosomal RNA and ribosomal proteins appears tightly coupled during the transition from growth to starvation. In long-time-starved cells the synthesis of ribosomal RNA and ribosomal proteins are stoichiometrically balanced with no significant degradation of de novo synthesized ribosomal proteins.

Animals↗
PubMed1984

Regulation of ribosome synthesis in Tetrahymena pyriformis. 2. Coordination of synthesis of ribosomal proteins and ribosomal RNA during nutritional shift-up.

The addition of nutrients to long-time-starved cells of Tetrahymena pyriformis leads to a 50-60-fold increase in the rate of synthesis of ribosomal proteins (r-proteins). This is achieved by a 6-fold increase in the relative rate of r-protein synthesis and a 8-10-fold increase in the rate of total protein synthesis. Synthesis of r-proteins constitutes one third of total cellular protein synthesis 2-4 h after refeeding and the absolute rate of r-protein synthesis is approximately three-times greater than in exponentially growing cells. The synthesis of the individual r-proteins is coordinately regulated during a nutritional shift-up, and de novo synthesized r-proteins are stable. Addition of actinomycin D prevents the increase in the rate of r-protein synthesis. The rates of synthesis of rRNA and r-protein increase in concert, implying coordinate regulation. Furthermore, a comparison of the observed accumulation of r-proteins with the predicted accumulation based on the accumulation of rRNA suggests that rRNA and r-protein are synthesized in a stoichiometrically balanced way during the entire refeeding period.

Animals↗
PubMed1984

Regulation of ribosome synthesis in Tetrahymena pyriformis. 3. Analysis by translation in vitro of RNA isolated during nutritional shift-down and nutritional shift-up.

We have measured the levels of translatable total mRNA and ribosomal protein (r-protein) mRNAs in Tetrahymena pyriformis during nutritional shifts. After 15 min of starvation total mRNA is reduced 2-fold, and after 24 h 7.5-fold, relative to exponentially growing cells. Upon refeeding total mRNA increases rapidly reaching the level of exponentially growing cells after 2.5 h. The levels of the individual r-protein mRNAs are coordinately regulated throughout a starvation-refeeding cycle. The relative levels of r-protein mRNAs remain virtually unchanged during the first hour of starvation and then decrease gradually to 30% of the relative levels in exponentially growing cells. Following refeeding the relative levels of r-protein mRNAs increase 6-fold. Taking into account the changes in whole cell RNA, we have calculated that long-time-starved Tetrahymena cells contain only 4%, whereas cells after 3 h of refeeding contain 200% of the amount of r-protein mRNA in exponentially growing cells. The amount of r-protein mRNA thus increases 50-fold during the first 3 h of refeeding. A comparison between the relative levels of r-protein mRNAs and the relative rate of r-protein synthesis in vivo indicates that Tetrahymena employs a combination of control of translation and control of the level of r-protein mRNAs to ensure a rapid reduction in the rate of r-protein synthesis during the early period of starvation. In this period translation of r-protein mRNAs is preferentially inhibited. During refeeding the increase in the rate of r-protein synthesis parallels the increase in the abundance of r-protein mRNAs.

Animals↗