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P Toivanen

Publications and source records attributed to P Toivanen.

At least 91 records · Page 5Linked to original sources
PubMed1995

A novel locus of Yersinia enterocolitica serotype O:3 involved in lipopolysaccharide outer core biosynthesis.

Yersinia enterocolitica serotype O:3 strain 6471/76-c (YeO3-c) was sensitive to bacteriophage phi R1-37 when grown at 37 degrees C but not when grown at 22 degrees C because of steric hindrance by abundant lipopolysaccharide (LPS) O-side chain (O-antigen) expressed at 22 degrees C. The transposon library of YeO3-c was grown at 37 degrees C and screened for phage phi R1-37-resistant transposon insertion mutants. Three types of mutant were isolated: (i) phage receptor mutants expressing O-antigen (LPS-smooth), (ii) phage receptor mutants not expressing O-antigen (LPS-rough), and (iii) LPS-smooth mutants with the phage receptor constitutively sterically blocked. Mutant type (i) was characterized in detail; the transposon insertion inactivates an operon, named the trs operon. The main findings based on this mutant are: (i) the frs operon is involved in the biosynthesis of the LPS outer core in YeO3-c; the nucleotide sequence of the trs operon revealed eight novel genes showing similarly to known polysaccharide biosynthetic genes of various Gram-negative bacteria as well as to capsule biosynthesis genes of Staphylococcus aureus; (ii) the biosynthesis of the core of YeO3-c involves at least two genetic loci; (iii) the trs operon is required for the biosynthesis of the bacteriophage phi R1-37 receptor structures; (iv) the homopolymeric O-antigen of YeO3-c is ligated to the inner core in Y. enterocolitica O:3; (v) the trs operon is located between the adk-hemH and galE-gsk gene pairs in the Y. enterocolitica chromosome; and (vi) the phage phi R1-37 receptor is present in many but not in all Y. enterocolitica serotypes. The results also allow us to speculate that the trs operon is a relic of the ancestral rfb region of Y. enterocolitica O:3 carrying genes indispensable for the completion of the core polysaccharide biosynthesis.

Amino Acid Sequence↗
PubMed1995

Characterization of chicken CD8-specific monoclonal antibodies recognizing novel epitopes.

CD8 is a heterodimeric cell surface glycoprotein expressed primarily on thymocytes and a subpopulation of mature T lymphocytes. It binds to the invariant part of the major histocompatibility complex class I molecule and participates in antigen recognition by the major histocompatibility complex class I restricted T cells. As in mammalian species, the majority of chicken thymocytes express both CD4 and CD8, whereas peripheral T cells are either CD4- or CD8-positive. We have created a panel of mouse monoclonal antibodies detecting different cell surface epitopes on chicken CD8. The antibodies precipitate a 32-34 kDa dimeric protein from surface labelled thymocytes under reducing conditions. The identical N-deglycosylation pattern confirms that these MoAb precipitate the same heterodimeric molecule from chicken thymocyte lysates. Binding of 11-38 and 11-39 MoAb to peripheral blood T cells is totally inhibited by 11-39 and previously characterized CT8 and EP72 MoAb, further confirming their CD8 specificity. CD8 alpha-chain specificity of MoAb 11-39, 11-38, 11-30 and 11-13 is conclusively proven by staining COS-cells transfected with a plasmid containing CD8 alpha cDNA. However, MoAb 11-13, 11-30 and 11-38 do not compete with MoAb 11-39 in binding to CD8. These results demonstrate recognition of different epitopes by these MoAb. Monoclonal antibodies detecting novel epitopes on chicken CD8 provide a valuable tool for further studies on T cell development.

Animals↗
PubMed1995

Usage of beta 1 integrin ligands by B cells is developmentally regulated in avian bursa.

Chicken B cell development takes place in a separate organ, the bursa of Fabricius, which provides the blood-borne stem cells, a microenvironment specialized for B cell maturation. Therefore, chicken can be used as a model to study specifically the molecules and interactions which control the development of the B cell compartment. In this work, we studied expression, localization and function of beta 1 integrins on maturing B cells and bursal stroma. The expression of beta 1 integrins on B cells increases during the embryonic development and beta 1 integrin-positive cells can be found both in the medulla and the cortex throughout the bursal development. The binding assays show that the attachment of B cells to stroma is mediated by beta 1 integrins. Binding to 10-day-old embryonic stroma is fibronectin-independent, whereas fibronectin-mediated binding takes place in an increasing manner during further embryonic maturation. After hatching fibronectin appears to be the main binding site for B cells. However, the epitope of beta 1 integrin which takes part in the adhesion of B cells to stroma and to fibronectin is not crucial for the homing of cells into the bursa in a cell transfer model. Our results indicate that the interaction of beta 1 integrins with their ligands is developmentally regulated in the bursa and suggest that B cell maturation may be partially controlled by this interaction.

Amino Acid Sequence↗
PubMed1995

Role of YadA-mediated collagen binding in arthritogenicity of Yersinia enterocolitica serotype O:8: experimental studies with rats.

Outer membrane protein YadA, Yersinia adhesin, is one of the plasmid-encoded virulence factors of yersiniae. YadA protects bacteria against host defense through several different mechanisms. One important role of YadA is to mediate binding to several collagen types. Our recent study revealed that a yadA null mutant of Yersinia enterocolitica serotype O:8 has a drastically reduced arthritogenic capacity when injected intravenously into Lewis rats. To further characterize the arthritogenic role of YadA, we repeated the rat experiments with strain Y. enterocolitica O:8/pYV082; this strain expresses a YadA deletion derivative lacking 22 amino acids from the amino-terminal hydrophobic region and does not bind to collagen. Y. enterocolitica O:8/pYV082 induced arthritis in 5 to 14% of rats inoculated with arthritogenic doses, whereas the arthritis incidence with the wild-type parent strain was 65%. The parent strain was slightly more virulent than Y. enterocolitica O:8/pYV082, as determined by rat mortality. It also frequently induced skin abscesses, whereas Y. enterocolitica O:8/pYV082 did not. Infection kinetics in spleen and mesenteric lymph nodes were about the same with both of the bacterial strains used, and the same was true of the Yersinia-specific antibody response. Altogether, these results suggest that YadA-mediated collagen binding contributes to the arthritogenicity of Y. enterocolitica O:8.

Adhesins, Bacterial↗
PubMed1995

Persistence of parvovirus B19 in synovial fluid and bone marrow.

OBJECTIVES: To determine whether parvovirus B19 (B19) persists in rheumatoid arthritis (RA). METHODS: Polymerase chain reaction (PCR) was used to detect parvovirus B19 genome in the synovial fluid cells or peripheral blood mononuclear cells from 61 patients with early RA; bone marrow from one patient was also studied. The synovium or synovial fluid cells from 28 patients with advanced RA, and synovial fluid cell samples from 18 patients with reactive arthritis (as controls) were studied. Two separate sets of primers and probe were used. RESULTS: Parvovirus B19 specific gene sequences were detected in two patients with early arthritis fulfilling the criteria for RA. CONCLUSION: Parvovirus B19 does not play a significant role in the aetiopathogenesis of RA. However, a few cases of a disease indistinguishable from RA may be triggered by parvovirus B19 infection.

Adult↗
PubMed1995

Effect of benzisoselenazolones and organic diselenides on graft versus host reaction and immunoglobulins levels in chickens.

Two week old chickens were treated once daily for 5 days with AE8--1-pyridyl-1,2-benzisoselenazol-3(2H)-one, AE22--bis-2-(N-phenyle-carboxamido) 1 pyridyl diselenide and AE31--bis(phenylo-diselenide with R3 = CONHC18H37). Their whole blood alone or blood mixed with thymus cells were used to generate graft versus host (GvH) reaction in 15 day old chicken embryos. The treatment of the chickens with the compounds stimulated the GvH reaction modifying activity of the donor cells as measured by increase of the spleen weight of the recipient chicken embryos. On the other hand, treatment with these compounds inhibited the IgG or IgM production in chickens immunized with human albumin.

Animals↗
PubMed1994

Intestinal flora in early rheumatoid arthritis.

To study the role of intestinal flora in the pathogenesis of RA, we have applied computerized gas-liquid chromatography (GLC) for bacterial cellular fatty acids (CFAs) present in the stool. The CFA spectra represents the total composition of bacterial CFAs in a faecal sample. Correlation and cluster analysis of CFA spectra gathers samples with quantitatively and qualitatively similar bacterial flora into clusters, which then reveal the relationship of samples to each other. Stool samples were collected at the time of hospital admission from patients with early RA before any specific treatment. The CFA spectra in stool samples of RA patients were significantly different from those of non-RA controls. Patients with erosive RA formed a group most clearly different from the controls. Analyses based on the CFA composition of reference bacteria revealed that anaerobic bacteria are primarily responsible for the differences observed. These results suggest that intestinal bacteria play a role in the development of RA.

Arthritis, Rheumatoid↗
PubMed1994

Changes of faecal flora in rheumatoid arthritis during fasting and one-year vegetarian diet.

The beneficial effect of a 1-yr vegetarian diet in RA has recently been demonstrated in a clinical trial. We have analysed stool samples of the 53 RA patients by using direct stool sample gas-liquid chromatography of bacterial cellular fatty acids. Based on repeated clinical assessments disease improvement indices were constructed for the patients. At each time point during the intervention period the patients in the diet group were then assigned either to a group with a high improvement index (HI) or a group with a low improvement index (LI). Significant alteration in the intestinal flora was observed when the patients changed from omnivorous to vegan diet. There was also a significant difference between the periods with vegan and lactovegetarian diets. The faecal flora from patients with HI and LI differed significantly from each other at 1 and 13 months during the diet. This finding of an association between intestinal flora and disease activity may have implications for our understanding of how diet can affect RA.

Arthritis, Rheumatoid↗
PubMed1994

Epidemiologic aspects, clinical features, and management of ankylosing spondylitis and reactive arthritis.

The generally reported prevalence of 0.1% to 0.2% for ankylosing spondylitis in the white population is probably too low, because it is based almost entirely on hospital records. The incidence and clinical presentation of ankylosing spondylitis have not changed during the past few decades. For reactive arthritis, the list of microbes recognized as triggering agents is continuously increasing. Reactive arthritis is divided into urogenic, enterogenic, respiratory tract-associated, and idiopathic arthritides. In addition, several microbial diseases may be accompanied by reactive arthritis, even though the identity of the causative agent is not always known. In the diagnosis of the spondyloarthropathies, definite progress has been made in developing classification criteria. Intensive research is going on to evaluate new therapies, with special attention to the use of antimicrobial agents for the treatment of reactive arthritis.

Arthritis, Reactive↗
PubMed1994

Gamma delta and alpha beta T cells are equally susceptible to apoptosis.

Little is known about the role of apoptosis in the regulation of gamma delta T cell development and function. We have used chicken as a model to study apoptosis of gamma delta T cells at different stages of their development. Apoptosis was measured with electrophoretic analysis of DNA fragmentation and flow cytometric determination of DNA content combined with immunofluorescence staining of cell surface molecules. In vitro culture, dexamethasone, and gamma-irradiation induced apoptosis of both gamma delta TCR+ thymocytes and peripheral gamma delta T cells. Apoptosis could be induced even in the earliest thymic gamma delta thymocytes on embryonic day 13. Resting peripheral blood gamma delta T cells were more resistant to apoptosis than thymocytes and spleen cells. Following polyclonal activation of splenic gamma delta T cells by Con A, the proportion of the CD8+ gamma delta T cell blasts decreased significantly when recultured without further stimulation. These results indicate that gamma delta T cells are susceptible to apoptosis in a manner similar to alpha beta T cells, and suggest that apoptosis plays an important role in the regulation of the development and function of both thymic and peripheral gamma delta T cells.

Animals↗
PubMed1994

Role of YadA in arthritogenicity of Yersinia enterocolitica serotype O:8: experimental studies with rats.

Outer membrane protein YadA, the Yersinia adhesin, is one of the plasmid-encoded virulence factors of yersiniae. To evaluate the role of YadA in the pathogenesis of reactive arthritis experimentally, we used YadA- strain YeO8-116, a kanamycin GenBlock insertion mutant derived from Yersinia enterocolitica O:8 wild-type strain 8081. As control strains, a plasmid-cured derivative (8081-c) of 8081 and a YopH- mutant (8081-yoph) were used. In addition, YeO8-116, with the yadA mutation transcomplemented with plasmid pMW10, was used. YeO8-116 induced arthritis to a considerably lesser extent than did wild-type strain 8081 when inoculated intravenously into Lewis rats. In rats surviving for over 14 days after the bacterial inoculation, the arthritis incidences were 6% (4 of 72) among those inoculated with the yadA mutant and 51% (33 of 65) among those inoculated with wild-type strain 8081. When the yadA gene was transcomplemented back to YeO8-116, YeO8-116/pMW10 induced arthritis in 47% (9 of 19) of the inoculated rats. Plasmid-cured strain 8081-c did not induce arthritis in any of the 24 inoculated rats, whereas YopH- mutant 8081-yoph induced arthritis in 20% (5 of 25) of the rats inoculated. Although the 50% lethal dose of YeO8-116 was about sixfold higher than that of 8081, the kinetics of bacterial elimination from the spleen and mesenteric lymph nodes were about the same with both strains. Antibody responses in rats infected with the two strains were also indistinguishable. Our results indicate that YadA contributes to the arthritogenicity of Y. enterocolitica in the rat model.

Adhesins, Bacterial↗
PubMed1994

YadA mediates specific binding of enteropathogenic Yersinia enterocolitica to human intestinal submucosa.

The binding of live Yersinia enterocolitica to frozen sections of human intestine was investigated qualitatively by monitoring the binding of bacteria by using Gram or immunoperoxidase staining as well as quantitatively by a new enzyme immunoassay-on-slide method. We have demonstrated that the binding of various Y. enterocolitica serotypes and Escherichia coli clones to frozen sections of human intestine is mediated by the Yersinia adhesin, YadA. The YadA-mediated binding occurs mainly at the submucosal layer of the intestinal wall and only to a limited extent at the mucosal layer; there binding is mostly to the mucin threads. In addition, partially purified YadA binds to frozen sections with a pattern similar to that of intact bacteria. Collagen, laminin, or partially purified YadA only partially inhibited the YadA-mediated binding of bacteria, presumably because YadA is multifunctional. A combination of collagen and laminin inhibited the binding more efficiently. Therefore, YadA may be involved in the interactions with the extracellular matrix molecules after the invasion of the intestinal tissue.

Adhesins, Bacterial↗