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S Johansen

Publications and source records attributed to S Johansen.

At least 55 records · Page 3Linked to original sources
PubMed1994

An intron in the nuclear ribosomal DNA of Didymium iridis codes for a group I ribozyme and a novel ribozyme that cooperate in self-splicing.

We have discovered a unique group I intron-like insertion (DiSSU) in the nuclear small subunit ribosomal RNA gene of the myxomycete Didymium iridis. By sequence, DiSSU consists of a group I ribozyme at the 5' end, an open reading frame (ORF) in the middle, and a novel element at the 3' end. Intron RNA self-splices in vitro to yield ten major processed RNAs, including a full-length circle. The group I ribozyme can efficiently cleave at an internal processing site, which separates the group I ribozyme from the ORF. Surprisingly, deletion that remove the entire group I ribozyme do not impair cleavage at the 3' splice site, implying that the 3' element itself is a catalytic RNA. Deletions that remove portions of the 3' element prevent utilization of the 5' splice site, suggesting that this element cooperates with the upstream group I ribozyme in splicing. DiSSU appears to be the first example for the cooperative interaction of distinct ribozymes in RNA splicing.

Amino Acid Sequence↗
PubMed1994

Intraocular T-cell lymphoma mimicking a ring melanoma. First manifestation of systemic disease. Report of a case and survey of the literature.

A case is presented of an intraocular T-cell lymphoma mimicking a ring melanoma of the iris and being the first manifestation of systemic disease. A 51-year-old woman was referred with an anterior uveitis, initially presenting as a granulomatous iritis. Nodules had developed in the circumference and the lesion now imitated a malignant melanoma of the iris, which was also the diagnosis from a biopsy specimen with routine staining. Clinical, haematological and serological examination revealed no other symptoms or signs. Lymphocytic markers applied to the biopsy specimen and to the enucleated eye revealed a highly malignant T-cell lymphoma infiltrating the iris, ciliary body, anterior choroid, retina and the adjacent vitreous body. Further examination later showed T-cell lymphoma in the bone marrow, the only other organ involved. The patient died in a leukaemic phase about 1 year after the first admission. Previous cases of T-cell lymphoma with ocular involvement are reviewed.

Ciliary Body↗
PubMed1994

Intragenic rearrangements in the mitochondrial NADH dehydrogenase subunit 6 gene of vertebrates.

We have sequenced the mitochondrial-encoded NADH dehydrogenase subunit 6 gene from 19 species of birds. Comparison of the derived amino-acid sequences in 22 avian species, six mammals, and two fishes, reveals an intragenic rearrangement in mammals. The C-terminal half of the mammalian protein includes an internal insertion of 10-15 amino acids and a C-terminal deletion of 8-9 amino acids. Based on comparative sequence alignments and hydropathy profile analysis, five hydrophobic segments (designated I to V) corresponding to transmembrane regions are proposed. In this structural model of NADH dehydrogenase subunit 6, the mammalian insertion is found in a variable loop region between transmembrane segments IV and V.

Amino Acid Sequence↗
PubMed1993

The framing effect of relative and absolute risk.

OBJECTIVE: To test whether a patient's perception of benefit is influenced by whether the benefit is presented in relative or absolute terms. DESIGN: Questionnaire-based study. SETTING: A general medicine outpatient clinic at a rural tertiary care center associated with a medical school. PATIENTS: 470 of 511 consecutive patients who agreed to answer a questionnaire while waiting for their clinic visit. Mean age was 49.1 years, 62.1% were female, and 51.9% had at least one year of education beyond high school. MAIN OUTCOME MEASURES: Patient response to the choice of two equally efficacious medications for the management of a hypothetical serious disease. The benefit of one medication was stated in relative terms, the other in absolute terms. Patients could choose either medication alone, indicate indifference to the choice of medication, or choose not to answer. MAIN RESULTS: 56.8% of the patients chose the medication whose benefit was in relative terms. 14.7% chose the medication whose benefit was in absolute terms. Only 15.5% were indifferent to the choice of medication. The patients preferred the medication whose benefit was in relative terms across a wide range of ages and educational levels. Further questioning suggested that the patients thought benefit was greater when expressed in relative terms because they ignored the underlying risk of disease and assumed it was one. CONCLUSIONS: The "framing" of benefit (or risk) in relative versus absolute terms may have a major influence on patient preference.

Adolescent↗
PubMed1993

Effect of selecting for increased lean tissue growth rate in swine on low or high dietary protein levels.

To determine the optimum nutritional status when selecting for increased daily lean tissue growth rate (LTGR) two selection lines of Swedish Yorkshire pigs were tested for responses and interactions when fed three diets that contained .70, .85, or 1.00% lysine and 13.9, 15.8, or 17.5% CP, respectively. Selection for increased LTGR was made while the pigs were fed diets with low CP (13.1%) and lysine (.64%) (LP line) or high CP (18.5%) and lysine (.96%) (HP line) concentrations. Two experiments were performed after three generations of selection, with pigs fed from 25 to 105 kg BW. The animals were fed restrictedly on an energy basis in relation to BW. A total of 236 pigs were tested. When testing main effects of selection line, the HP line had superior average daily lean tissue gain (P = .031), carcass lean percentage (P = .007), and lean to feed ratio (P = .028) compared with the LP line. No diet x genotype interaction was found for any of the traits tested. The selection in the HP line resulted in faster genetic progress because this line had best overall performance. This supports the theory that the most efficient selection is achieved in an environment that enables the animals to express their genetic capacity for the desired trait.

Adipose Tissue↗
PubMed1993

Adult idiopathic polymyositis without elevation of creatine kinase. Case report and review of the literature.

A patient fulfilling diagnostic criteria for definite polymyositis, but with normal levels of creatine kinase (CK) is reported. Review of the literature reveals significant variations regarding the frequencies of normal CK reported among cases with myositis. The discrepancies may be partly explained by inclusion of both probable and possible polymyositis, administration of steroid therapy prior to estimations of CK, and possible differences in CK levels between polymyositis and dermatomyositis. The patient reported did not suffer from neither lung disease nor concomitant malignancy. Thus, the alleged association between low levels of CK and poor prognosis in myositis could not be supported by the present case report.

Creatine Kinase↗
PubMed1993

The putative origin of heavy strand replication (oriH) in mitochondrial DNA is highly conserved among the teleost fishes.

We have determined the nucleotide sequence of a 645 bp EcoRI-HindIII fragment from mitochondrial DNA of Arctic charr, Salvelinus alpinus. The sequence includes the tRNA(Phe) gene, part of the small subunit ribosomal RNA gene as well as the putative origin of heavy strand replication located at the major non-coding region, the D-loop containing region. Upon comparison of the Arctic charr sequence to mitochondrial DNA sequences from several distantly related teleost fishes, the origin of heavy strand replication was found to be highly conserved among the teleost fishes.

Animals↗
PubMed1992

Characterization of the self-splicing products of a mobile intron from the nuclear rDNA of Physarum polycephalum.

We have characterized the splicing products formed in vitro from RNA derived from the mobile group I intron in the nuclear rDNA of Physarum polycephalum, Pp LSU 3. This intron is a close relative of the well known Tetrahymena intron Tt LSU 1, being inserted at exactly the same position in the rDNA and sharing about 90% sequence identity with Tt LSU 1 in the conserved elements characteristic of the catalytic core of all group I introns. However, Pp LSU 3 differs from Tt LSU 1 in that it encodes a site-specific endonuclease, which mediates the homing of the intron to unoccupied target sites. The endonuclease, I-Ppo, would appear to be a unique example of a protein encoded by an RNA polymerase I transcript. To gain clues to the splicing products formed in vivo, and to the nature of the messenger RNA for I-Ppo, we subjected Pp LSU 3 RNA to standard self-splicing conditions in vitro, and then analyzed the products by size, by northern blotting, and by primer extension. The results show two novel features. First, in addition to the expected 5' splice site, there is an alternative 5' splice site in the upstream exon, just preceding the first codon of the I-Ppo open reading frame. Second, at the position corresponding to the major circularization site in Tt LSU 1 there is an internal processing site, leading to the efficient separation of two halves of the excised intron, the 5' half encoding I-Ppo and 3' half containing the ribozyme. Surprisingly, this cleavage appears not to be due to circularization followed by hydrolytic opening of the circle, but rather to G addition. The formation of these products in vitro suggests how the messenger RNA for the I-Ppo endonuclease may be generated in vivo.

Animals↗
PubMed1992

Structure and evolution of myxomycete nuclear group I introns: a model for horizontal transfer by intron homing.

We have examined five nuclear group I introns, located at three different positions in the large subunit ribosomal RNA (LSU rRNA) gene of the two myxomycete species, Didymium iridis and Physarum polycephalum. Structural models of intron RNAs, including secondary and tertiary interactions, are proposed. This analysis revealed that the Physarum intron 2 contains an unusual core region that lacks the P8 segment, as well as several of the base-triples known to be conserved among group I introns. Structural and evolutionary comparisons suggest that the corresponding introns 1 and 2 were present in a common ancestor of Didymium and Physarum, and that the five introns in LSU rRNA genes of these myxomycetes were acquired in three different events. Evolutionary relationships, inferred from the sequence analysis of several different nuclear group I introns and the ribosomal RNA genes of the intron-harbouring organisms, strongly support horizontal transfer of introns in the course of evolution. We propose a model that may explain how myxomycetes in natural environments obtained their nuclear group I introns.

Animals↗
PubMed1992

Extrachromosomal ribosomal DNA of Didymium iridis: sequence analysis of the large subunit ribosomal RNA gene and sub-telomeric region.

The ribosomal DNA of the myxomycete Didymium iridis is organized as extrachromosomal linear molecules of about 20 kb, containing only one transcription unit of the ribosomal RNA genes. We have determined the sequence of the large subunit ribosomal RNA (LSU rRNA) gene as well as the sub-telomeric and telomeric regions. The LSU rRNA gene was found to encode a 3857 nucleotide-long LSU rRNA, interrupted by a transcribed spacer and two group I introns. A complete secondary structure model of D. iridis LSU rRNA has been constructed. The compact sub-telomeric region of D. iridis rDNA was found to contain several directly repeated sequence elements that include the simple telomere motif TTAGGG. Based on pairwise comparisons of LSU rRNA sequences, the time of divergence between the two myxomycete genera Didymium and Physarum was estimated.

Animals↗
PubMed1992

The mitochondrial NADH dehydrogenase subunit 6 (ND6) gene in Murres: relevance to phylogenetic and population studies among birds.

The nucleotide sequences of the mitochondrial ND6 and tRNA(Glu) genes and part of the displacement loop region in two closely related seabird species are presented. A chicken type gene organization in which the tRNA(Glu), ND6, and displacement loop are localized next to each other was found in these species and suggests that this is a conserved feature of avian mitochondrial DNA. The nucleotide and amino acid divergences of ND6 at different taxonomic levels are assessed, and its relevance to phylogenetic studies in birds is discussed.

Amino Acid Sequence↗
PubMed1991

[Anti-cardiolipin antibody in cerebral infarction].

A 28 year old woman with a previous history of labile hypertension, migraine and transitory cerebral ischemia was admitted with cerebral infarction. One month later she developed livedo reticularis and amaurosis fugax, which led to the diagnosis of Sneddon's disease (livedo reticularis, labile hypertension and neurological symptoms) and the anticardiolipin antibody (ACA) syndrome. Treatment with prednisone and phenprocoumon resulted in lowering of ACA-titers, but the symptoms did not subside until acetylsalicylic acid was added.

Adult↗
PubMed1991

[Antiphospholipid antibodies].

Antiphospholipid antibodies (APA) are acquired, circulating immunoglobulins connected with thrombo-embolic diseases occurring within all organ systems. Whether the antibodies are of pathogenetic relevance for the development of thrombo-embolic states is unresolved. All materials are limited and have yielded contradictory results with regard to important aspects. An increased APTT or PTT does not increase the risk of bleeding in patients with LA, unless abnormalities in the coagulation process are present, e.g. thrombocytopenia or hypoprothrombinaemia. Many questions are unanswered: Should APA be treated in asymptomatic patients? Should patients with APA and relevant symptoms be treated? If so, which treatment should be chosen? And how long should the treatment continue? Are APA of pathogenetic importance or are they markers for another mechanism that causes an immunocoagulopathy? How can it be explained that so many persons produce autoantibodies without becoming seriously ill? In order to clarify the significance of APA it is necessary to standardize tests and to perform extensive, prospective studies, where variations of ACA titres are analysed. Until results from such studies are available, APA should be looked for in patients with recurring arterial or venous thrombosis and in patients with recurring spontaneous abortion with reference to anticoagulant and anti-platelet aggregation therapy if IgG-ACA are elevated over prolonged periods.

Autoantibodies↗
PubMed1991

Rapid disappearance of one parental mitochondrial genotype after isogamous mating in the myxomycete Physarum polycephalum.

Five haploid amoebal strains of the myxomycete Physarum polycephalum, each with a distinct mitochondrial genotype, were crossed in all pairwise combinations. The mitochondrial genotype in the diploid plasmodia resulting from these isogamous matings were found to be transmitted uniparentally. This uniparental inheritance could be arranged in a dominant hierarchical order. Time-course analysis of the presence of mitochondrial genotypes in the zygotes and young developing plasmodia show that elimination of one parental mitochondrial genotype is virtually completed during the first two nuclear cycles in the zygote/differentiating plasmodium. To our knowledge this is the first report indicating an active mechanism involving the degradation of mitochondrial genomes in sexual crosses.

Crosses, Genetic↗
PubMed1991

Strain-dependent sequence heterogeneity in the nuclear group I introns and large subunit ribosomal RNA in Physarum polycephalum.

The DNA sequence of an internal EcoRI fragment in the large subunit ribosomal RNA gene from the myxomycete Physarum polycephalum, strain M3C, has been determined. This ribosomal DNA fragment contain two group I introns. Sequence heterogeneity in the two introns and in the coding region of the ribosomal RNA were identified upon comparison to the strain PPO-1 sequence. The nature of the sequence variations is discussed.

Animals↗