| 1. |
- Alksnis, M., et al.
(författare)
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Use of synthetic oligodeoxyribonucleotides for type-specific identification of coxsackie B viruses
- 1989
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Ingår i: Molecular and Cellular Probes. - : Elsevier BV. - 0890-8508 .- 1096-1194. ; 3:2, s. 103-108
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Tidskriftsartikel (refereegranskat)abstract
- Synthetic oligodeoxyribonucleotides were used for type-specific identification of members of the coxsackie B virus group by nucleic acid hybridization. Two pairs of oligonucleotide chains were constructed based on nucleotide sequences in the VP1 regions of coxsackieviruses B3 and B4. Each labelled probe had a length of 24 nucleotides. The results showed that the oligonucleotide hybridized in a type-specific manner when assayed with extracts from cells infected with all different coxsackie B viruses. A method based on similar principles may thus be used for enterovirus typing.
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| 2. |
- Anna, B., 1960-, et al.
(författare)
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Animal model of rotavirus infection in rabbits - protection obtained without shedding of viral antigen.
- 1989
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Ingår i: Archives of Virology. - : Springer. - 0304-8608 .- 1432-8798. ; 107:3-4, s. 237-251
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Tidskriftsartikel (refereegranskat)abstract
- A small animal model was developed in order to investigate the pathogenesis and immunology of rotavirus infections and to study the interaction of different virus strains. Seronegative rabbits of the breed French Lop were used. Two rabbit rotavirus strains, belonging to the same serotype, were used: 82/311 F and R-2, both isolated during diarrhoeal outbreaks in commercial rabbitries. The animals were inoculated orally. The viral shedding and the serological response was monitored by ELISA. Initially six weeks old kits were given four different doses of strain R-2. With doses ranging from 1 x 10(3) to 1 x 10(6) TCID50 all animals seroconverted, but for the lowest dose no viral excretion could be detected. No clinical symptoms were observed. Subsequently the age periods during which the animals were susceptible to the strain R-2 was investigated. The rabbits seroconverted and shed rotavirus antigen, independent of age of six or 22 weeks. None of the animals had diarrhoea. Administration of strain 82/311 F did not result in viral shedding, independently of dose, but all the animals seroconverted. It was also shown for the strain R-2 that when challenging with the same strain four weeks post inoculation that the animals were protected; no viral shedding was detected at the second infection. Strain 82/311 F gave protection against R-2 when the rabbits were challenged four weeks post inoculation.
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| 3. |
- Bergqvist, Åsa, et al.
(författare)
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Smittspridning av campylobacter inom fjäderfäslakteri
- 1986
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Ingår i: XV Nordiska veterinärkongressen – 15th Nordic Veterinary Congress, Stockholm 28/7–1/8 1986. - Stockholm : Sveriges Veterinärförbund. - 9178106435 ; , s. 355-358
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Konferensbidrag (refereegranskat)
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| 4. |
- Bergström, Sven, 1950-
(författare)
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Chromosomal β-lactamases in enterobacteria and in vivo evolution of β-lactam resistance
- 1983
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The ß-lactam antibiotics are the most important antibacterial agents in the treatment of infectious diseases. A severe problem in ß-lactam therapy is the emergence of ß-lactam resistant bacteria. Clinical ß-lactam resistance is most often due to the production of ß-lactamases. ß-lactamase genes reside either on plasmids or on the chromosome. The aim of this study was to acquire an understanding of organisation and regulation of chromosomal ß- lactamase genes in different Gram negative species and to elucidate the mechanisms for ampC hyperproduction in the in vivo situation.By DNA hybridization with an ampC probe from Escherichia coli K-12 it was shown that other Gram negative bacteria contained an artpC like chromosomal gene, suggesting a common evolutionary origin. Furthermore, the preceding frd operon that overlaps the ampC gene in E. coli K-12 was found to be much more conserved than the ampC gene in the bacterial species investigated.The ampC and frd opérons in Shigella sonnei and Citrobacter freundii were cloned and characterized by physical mapping. The respective maps were compared to the ampC and frd region in E. coli K-12. The physical map of Sh. sonnei was almost identical to the E. coli K-12 map, whereas in C. freundii only the frd region exhibited any considerable homology. Moreover, in C. freundii, the anpC and frd regions were separated by 1100 basepairs. It is suggested that this DNA is involved in the induction of ß-lactamase production in this organism. A hypothesis for the evolution of the anpC operon in enterobacteria is presented.By isolating and characterizing six ß-lactam resistant clinica], isolates of E. coli hyperproducing the dhrcmosomal ß-lactamase, genetic mechanisms for in vivo evolved resistance was aimed at. These isolates exhibited a 24-48 fold increase in ß-lactamase production. The ß-lactamase produced was found to be biochemically and immunologically identical to the ß-lactamase produced by E. coli K-12. The ampC control region of these six E. coli isolates was DNA-seqenced. The cause of ß-lactamase hyperproduction in five of the clinical E. coli isolates, identical in the DNA segment sequenced, was due to a strong novel ampC promoter displaced 5 bp upstream of the ampC promoter defined in E. coli K-12. The ß-lactamase hyperproduction in the sixth clinical isolate was shown to be caused by two mutations affecting both the promoter and the attenuator in the regulatory region defined by E. coli K- 12. The obtained changes were sufficient to explain the increase in ampC ß- 1 act ama se expression exhibited in these clinical E. coli isolates.Sequence analysis of the ampC control region in Sh. sonnei revealed that it was, with one exception, identical to the one found in the five clinical E. coli ß-lactamase hyperproducers. The only difference was in a position that creates the strong novel ampC promoter in the E. coli hyperproducers. By isolating spontaneous Sh. sonnei mutants with a 40-fold increase in ß-lactamase production carrying the same novel ampC promoter as the clinical E. coli isolates it was concluded that this DNA segment has been transferred in vivo frcm Shigella to E. coli across the species barrier.
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| 5. |
- Berndtson, Eva, et al.
(författare)
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Incidence of campylobacter on a broiler farm
- 1987
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Ingår i: The IVth International Workshop on Campylobacter Infections, Department of Clinical Bacteriology, University Göteborg, June 16–18, 1987, Göteborg, Sweden. ; , s. Abstract no. 17-
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Konferensbidrag (refereegranskat)
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| 6. |
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| 7. |
- Bredberg, Anders, et al.
(författare)
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4-quinolone antibiotics : Positive genotoxic screening tests despite an apparent lack of mutation induction
- 1989
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Ingår i: Mutation Research - Fundamental and Molecular Mechanisms of Mutagenesis. - : Elsevier BV. - 1879-2871 .- 0027-5107. ; 211:1, s. 171-180
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Tidskriftsartikel (refereegranskat)abstract
- The effects of different 4-quinolone antibiotic derivatives (4-Qs) in a number of short-term tests commonly employed for the evaluation of genetic toxicity were studied. Incorporation of [3H]thymidine into mitogen-stimulated peripheral blood lymphocytes was strongly enhanced at a low concentration (1.56 μg/ml) for most of the tested 4-Qs, whereas DNA strand breakage in lymphoblastoid cells was evident only for ciprofloxacin (10 μg/ml and upwards), ofloxacin (80 μg/ml) and norfloxacin (160 μg/ml). Ciphrofloxacin induced a significant amount of unscheduled DNA synthesis, but was found to be negative in a shuttle vector plasmid mutation test. Ciprofloxacin (80 μg/ml) did not inhibit enzymes involved in the early steps of pyrimidine biosynthesis. Cell growth was slightly depressed at a concentration of 20 μg/ml, becoming marked at 80 μg/ml. In conculsion, this study seeks to contribute to an improved evaluation of genotoxic screening test data, by focuding attention on the conflicting effects imposed by the 4-Qs on a battery of such tests.
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| 8. |
- Byström, Anders S., et al.
(författare)
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A functional analysis of the repeated methionine initiator tRNA genes (IMT) in yeast
- 1989
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Ingår i: Molecular General Genetics. - 0026-8925 .- 1432-1874. ; 216:2-3, s. 276-286
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Tidskriftsartikel (refereegranskat)abstract
- Standard laboratory yeast strains have from four to five genes encoding the methionine initiator tRNA (IMT). Strain S288C has four IMT genes with identical coding sequences that are colinear with the RNA sequence of tRNA(IMet). Each of the four IMT genes from strain S288C is located on a different chromosome. A fifth IMT gene with the same coding sequence is present in strain A364A but not in S288C. By making combinations of null alleles in strain S288C, we show that each of the four IMT genes is functional and that tRNA(IMet) is not limiting in yeast strains with three or more intact genes. Strains containing a single IMT2, 3 or 4 gene grow only after amplification of the remaining IMT gene. Strains with only the IMT1 gene intact are viable but grow extremely slow; normal growth is restored by the addition of another IMT gene by transformation, providing a direct test for IMT function.
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| 9. |
- Byström, Anders S, et al.
(författare)
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Differentially expressed trmD ribosomal protein operon of Escherichia coli is transcribed as a single polycistronic mRNA species
- 1989
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Ingår i: Journal of Molecular Biology. - : Academic Press. - 0022-2836 .- 1089-8638. ; 208:4, s. 575-586
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Tidskriftsartikel (refereegranskat)abstract
- The trmD operon is a four-cistron operon in which the first and fourth genes encode ribosomal proteins S16 (rpsP) and L19 (rplS), respectively. The second gene encodes a 21,000 Mr polypeptide of unknown function and the third gene (trmD) encodes the enzyme tRNA(m1G37)methyltransferase, which catalyzes the formation of 1-methylguanosine (m1G) next to the 3' end of the anticodon (position 37) of some tRNAs in Escherichia coli. Here we show under all regulatory conditions studied, transcription initiates at one unique site, and the entire operon is transcribed into one polycistronic mRNA. Between the promoter and the first gene, rpsP, an attenuator-like structure is found (delta G = -18 kcal; 1 cal = 4.184 J), followed by four uridine residues. This structure is functional in vitro, and terminates more than two-thirds of the transcripts. The different parts of the trmD operon mRNA decay at a uniform rate. The stability of the trmD mRNA is not reduced with decreasing growth rate, which is in contrast to what has been found for other ribosomal protein mRNAs. Furthermore, earlier experiments have shown the existence of differential expression as well as non-co-ordinate regulation within the operon. Our results are consistent with the regulation of the trmD operon being due to some mechanism(s) operating at the post-transcriptional level, and do not involve differential degradation of different mRNA segments, internal promoters or internal terminators.
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| 10. |
- Byström, Anders S, et al.
(författare)
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The nucleotide sequence of an Escherichia coli operon containing genes for the tRNA(m1G)methyltransferase, the ribosomal proteins S16 and L19 and a 21-K polypeptide
- 1983
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Ingår i: EMBO Journal. - : Oxford University Press. - 0261-4189 .- 1460-2075. ; 2:6, s. 899-905
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Tidskriftsartikel (refereegranskat)abstract
- The nucleotide sequence of a 4.6-kb SalI-EcoRI DNA fragment including the trmD operon, located at min 56 on the Escherichia coli K-12 chromosome, has been determined. The trmD operon encodes four polypeptides: ribosomal protein S16 (rpsP), 21-K polypeptide (unknown function), tRNA-(m1G)methyltransferase (trmD) and ribosomal protein L19 (rplS), in that order. In addition, the 4.6-kb DNA fragment encodes a 48-K and a 16-K polypeptide of unknown functions which are not part of the trmD operon. The mol. wt. of tRNA(m1G)methyltransferase determined from the DNA sequence is 28 424. The probable locations of promoter and terminator of the trmD operon are suggested. The translational start of the trmD gene was deduced from the known NH2-terminal amino acid sequence of the purified enzyme. The intercistronic regions in the operon vary from 9 to 40 nucleotides, supporting the earlier conclusion that the four genes are co-transcribed, starting at the major promoter in front of the rpsP gene. Since it is known that ribosomal proteins are present at 8000 molecules/genome and the tRNA-(m1G)methyltransferase at only approximately 80 molecules/genome in a glucose minimal culture, some powerful regulatory device must exist in this operon to maintain this non-coordinate expression. The codon usage of the two ribosomal protein genes is similar to that of other ribosomal protein genes, i.e., high preference for the most abundant tRNA isoaccepting species. The trmD gene has a codon usage typical for a protein made in low amount in accordance with the low number of tRNA-(m1G)methyltransferase molecules found in the cell.
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