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Biomedical subjects

A Vaheri

Publications and source records attributed to A Vaheri.

At least 91 records · Page 5Linked to original sources
PubMed1998

Association of ezrin with intercellular adhesion molecule-1 and -2 (ICAM-1 and ICAM-2). Regulation by phosphatidylinositol 4, 5-bisphosphate.

Ezrin is a cytoplasmic linker molecule between plasma membrane components and the actin-containing cytoskeleton. We studied whether ezrin is associated with intercellular adhesion molecule (ICAM)-1, -2, and -3. In transfected cells, ICAM-1 and ICAM-2 colocalized with ezrin in microvillar projections, whereas an ICAM-1 construct attached to cell membrane via a glycophosphatidylinositol anchor was uniformly distributed on the cell surface. An interaction of ICAM-2 and ezrin was seen by affinity precipitation, microtiter binding assay, coimmunoprecipitation, and surface plasmon resonance methods. The calculated KD value was 3.3 x 10(-7) M. Phosphatidylinositol 4, 5-bisphosphate (PtdIns(4,5)P2) induced an interaction of ezrin and ICAM-1 and enhanced the interaction of ezrin and ICAM-2, but ICAM-3 did not bind ezrin even in the presence of PtdIns(4,5)P2. PtdIns(4, 5)P2 was shown to bind to cytoplasmic tails of ICAM-1 and ICAM-2, which are the first adhesion proteins demonstrated to interact with PtdIns(4,5)P2. The results indicate an interaction of ezrin with ICAM-1 and ICAM-2 and suggest a regulatory role of phosphoinositide signaling pathways in regulation of ICAM-ezrin interaction.

Animals↗
PubMed1998

Evaluation of Puumala virus IgG and IgM enzyme immunoassays based on recombinant baculovirus-expressed nucleocapsid protein for early nephropathia epidemica diagnosis.

BACKGROUND: Puumala virus (PUU), a member of Hantavirus genus, is the causative agent of nephropathia epidemica (NE), a milder form of hemorrhagic fever with renal syndrome (HFRS). Rapid diagnosis is essential for clinical management of NE. OBJECTIVES: To evaluate the usefulness of recombinant protein-based IgM (direct- and mu-capture) and IgG (direct-and antigen (Ag)-capture) enzyme immunoassays (EIA) in early diagnosis of NE in comparison to IgG immunofluorescence assay (IF), and to find out the time limit for PUU-specific antibody seroconversion. STUDY DESIGN: The specific IgM and IgG antibody responses in serum were analyzed in 109 patients (235 serial sera) and 114 patients (233 serial sera), respectively. The serum panel used was selected from a larger material according to the availability of information concerning the date after onset of symptoms, the panel also containing NE patients who had been IgG-IF negative in their first (early) samples to find out the possible differences between sensitivities of the EIAs and IF. RESULTS: All NE patients tested became IgM-positive at the latest on the 6th (mu-capture EIA) or 7th (direct-IgM EIA) day after onset of symptoms. Out of a panel of very early NE-patient sera (n = 38) that could not be detected by IgG-IF, 66% were already positive with both direct-IgM EIA and mu-capture EIA. When comparing IgG EIAs and IgG-IF, 98% of IF-positive sera from NE patients were also positive with direct-IgG EIA, and 99% with Ag-capture IgG EIA. Out of a panel of very early NE-patient sera (n = 37) that could not be detected by IgG-IF, 57% were positive with direct-IgG EIA, and 27% with Ag-capture IgG EIA. CONCLUSIONS: The baculovirus-expressed PUU-N-based IgG and IgM EIAs were found most suitable for NE diagnosis, giving the opportunity in some cases for earlier diagnosis as compared with PUU-IgG IF.

Adolescent↗
PubMed1998

Pathogenesis of puumala and other hantavirus infections.

Hantaviruses are rodent/insectivore-borne negative-stranded RNA viruses which belong to the Bunyaviridae family. They do not cause any symptomatic disease in their adult carrier rodents, but in humans they are aetiologic agents of haemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS), both associated with a significant mortality. In cell culture hantaviruses do not cause cytopathic effects and the mechanisms of disease in man are not well understood. Increased capillary permeability is a central phenomenon in the pathogenesis of hantavirus infections. Although the viruses have in vivo a predilection for endothelial cells, it is presumed that inflammatory mediators of the host immune response play a significant role in the capillary leak that may produce abrupt hypotension and shock in severely ill patients. Mediators released by activated macrophages including NO and TNF-alpha are considered important. The pathogenesis of renal failure in HFRS also awaits to be resolved. This review summarises what is known about these phenomena and discusses also the molecular basis of the putative virulence factors of hantaviruses. Finally, the genetic predisposition and HLA association with severe Puumala virus infection will be discussed. Copyright 1998 John Wiley & Sons, Ltd.

Journal Article↗
PubMed1998

Genomic structure of the human ezrin gene.

The ERM proteins, ezrin, radixin, and moesin, act as linkers between the plasma membrane and actin cytoskeleton. They are involved in a variety of cellular functions, such as cell adhesion, migration, and the organization of cell surface structures, and are highly homologous, both in protein sequence and in functional activity, with merlin/schwannomin, a neurofibromatosis-2-associated tumor-suppressor protein. We report here the genomic structure and intron junction sequences of the human ezrin gene. Ezrin consists of 13 exons and spans approximately 24 kb genomic DNA. The coding parts of the exons range in size from 12 bp to 275 bp and the introns from 182 bp to 7 kb. The genomic structures of ezrin and moesin are highly conserved, suggesting their recent divergence. Radiation hybrid mapping has refined the location of ezrin to the interval between D6S442 and D6S281.

Amino Acid Sequence↗
PubMed1998

A novel method to culture laryngeal human papillomavirus-positive epithelial cells produces papilloma-type cytology on collagen rafts.

A novel method to culture human papillomavirus (HPV) positive laryngeal epithelial cells is described. Biopsies of laryngeal papillomas and of HPV-positive laryngeal mucosa were first cultured as a monolayer in which irradiated laryngeal fibroblasts originally derived from a papilloma (PPLF-XR) patient served as feeder cells. When these fourth or fifth passage epithelial cells were transferred to allow growth on an organotypic growth base (collagen raft containing unirradiated PPLF), they grew as a multilayer. This layer showed features typical of HPV infection with koilocytosis, parakeratosis, and isolated dyskeratotic cells. Based on in situ hybridisation, the original tumour sections and epithelial cells from each monolayer passage, as well as the collagen raft sections, contained HPV DNA. Our results show that HPV-infected epithelial cells can be maintained during passages in monolayer culture and that PPLF can support the growth of these cells well. The monolayer cell culture and the collagen raft, the latter providing differentiation-promoting effects, appears to facilitate maintenance of the infected cells and of the viral genome.

Animals↗
PubMed1998

Interferons and retinoids enhance and dexamethasone suppresses urokinase-mediated plasminogen activation in promyelocytic leukemia cells.

All-trans retinoic acid (RA) has been successfully used in the treatment of patients with acute promyelocytic leukemia (APL). It induces differentiation of APL cells and reduces the bleeding tendency in APL patients. It has been proposed that plasminogen activation could affect the fibrinolytic balance in patients with leukemia. In our earlier study we found that treatment of APL cells with RA results in changes in urokinase (uPA) production. As interferons (IFNs) and dexamethasone can be used together with RA in the treatment of patients with APL, we have now studied the effects of RA together with IFNs and dexamethasone on the plasminogen activation cascade of these cells, including measurement of plasmin generation and uPA receptor (uPAR), using enzyme immunoassays, fluorescence-activated cell sorter analysis and RNA extraction with Northern blotting. Our main results were: (1) plasmin was formed on the surface of APL cells; (2) RA stimulated transiently plasmin generation and increased uPAR mRNA level; (3) IFNs alpha and gamma potentiated RA in its effects on uPA and plasmin activities and on uPAR level; (4) dexamethasone suppressed totally the effect of RA on uPA induction and plasminogen activation; and (5) IFNs and dexamethasone alone did not have potent effects on plasminogen activation. These results may assist in the design of therapy for APL patients.

Antineoplastic Agents↗
PubMed1998

Association of HLA B27 with benign clinical course of nephropathia epidemica caused by Puumala hantavirus.

Both the severe course of nephropathia epidemica (NE) caused by Puumala hantavirus, and the fast progression of human immunodeficiency virus (HIV) disease, are associated with the HLA B8 DRB1*0301 haplotype. As HLA B27, on the contrary, is associated with the slow progression of HIV disease, we wanted to test whether the same is true for NE. Only six (8%) NE patients, half the figure expected, had the HLA B27 allele in 74 randomly selected hospital-treated patients. All six had a benign overall clinical course of NE; none had any severe complications, the severity of renal failure was also mild, and the treatment time at the hospital was half that needed for HLA B27- patients (P = 0.004). Patients who were HLA B27 had maximal blood leucocyte count > 10.000 x 10(9)/L (P = 0.020) more often, probably reflecting differences in immune response. Thus, similar HLA associations can be found in both HIV infection and NE caused by Puumala virus.

Adult↗
PubMed1998

High-producer allele of tumour necrosis factor-alpha is part of the susceptibility MHC haplotype in severe puumala virus-induced nephropathia epidemica.

The biallelic polymorphisms in the tumour necrosis factor-alpha (TNF-alpha) gene promoter region were studied in patients with nephropathia epidemica (NE). The rarer TNF2 allele, associated with a high TNF-alpha producer phenotype, was more frequently found in hospitalized NE patients (42%) than in healthy controls (15%; p=0.0064). The putative role of TNF2 as an independent risk factor for NE is discussed.

Alleles↗
PubMed1998

Isolation and characterization of Puumala hantavirus from Norway: evidence for a distinct phylogenetic sublineage.

Puumala (PUU) hantavirus is the aetiological agent of nephropathia epidemica (NE), a mild form of haemorrhagic fever with renal syndrome, which occurs in Fennoscandia, central Europe and Russia. In Norway, NE-like disease has been reported since 1946 and about 50 cases are diagnosed annually; however, the causative agent has not been characterized. In this study, a virus originating from bank voles (Clethrionomys glareolus) trapped near the town of Eidsvoll (Akershus county) was isolated and passaged in laboratory-bred bank voles. The bank vole strain was identified as a PUU virus by serological typing and by sequence analysis of the S and M gene segments. For comparison, complete or partial S sequences were determined for wild-type PUU strains from five locations in Sweden, two inhabited by the southern variant of bank vole present in Fennoscandia, and three by the northern variant. Phylogenetic analysis showed that Norwegian PUU strains are clustered together with Swedish strains from the first group forming a well-supported sublineage within the PUU genotype, distinct from other sublineages from northern Sweden, Finland, Russia and France. The results are consistent with the view of a complex evolutionary history of PUU strains in post-glacial Fennoscandia. Analyses of the current collection of nucleotide sequences suggest that PUU is the most variable genotype of the known hantaviruses.

Base Sequence↗
PubMed1998

Completion of the Tula hantavirus genome sequence: properties of the L segment and heterogeneity found in the 3' termini of S and L genome RNAs.

In this study the L segment and the 5' and 3' termini of the S, M and L segments of the prototype Tula hantavirus (TUL) were sequenced, thus completing the first determination of the genome sequence of a hantavirus that has not been linked to any human disease. The TUL L segment comprises 6541 nt with one ORF of 6459 nt in the antigenome sense. This ORF potentially encodes a 2153 aa protein with a predicted molecular mass of 247 kDa. The amino acid sequence includes all the motifs conserved in RNA-dependent RNA polymerases. The 5' termini of all three genome RNAs (vRNAs) had the expected sequences conserved in hantaviruses. The 3' termini of M vRNAs were also conserved. However, the 3' termini of S and L vRNAs were heterogeneous as most of the sequenced 3' termini had either deletions of 1 to 22 nt or an extra 1 to 3 nt. No increase in the level of heterogeneity was seen in vRNAs of virions collected 3, 6, 9 and 12 days post-infection, suggesting that the heterogeneity already exists at the early stages of infection. The S and L vRNAs from infected cells had more truncated 3' termini than vRNAs from pelleted virus. Heterogeneity of the 3' termini of genome RNAs could decrease the efficiency of antigenome and mRNA syntheses and contribute to the slow growth observed for TUL and other hantaviruses in cell culture.

Genome, Viral↗
PubMed1998

Human recombinant Puumala virus antibodies: cross-reaction with other hantaviruses and use in diagnostics.

A panel of seven human monoclonal Fabs against Puumala virus (PUU) nucleocapsid protein (N) was obtained by panning an antibody phage-display library prepared from the spleen of a PUU-immune individual. Three antibodies reacted in immunoblotting and cross-reacted strongly with Tula and Sin Nombre virus recombinant N proteins. These antibodies mapped to the amino terminus of the N protein. One PUU glycoprotein 2 (G2)-specific Fab obtained against a novel epitope (G2c) cross-reacted with Khabarovsk virus but not with the other hantavirus serotypes. An N protein-specific Fab was successfully used as capture antibody to detect PUU-specific serum IgG and IgM antibodies in an enzyme immunoassay. The result demonstrates the usefulness of recombinant human Fabs as potential diagnostic tools.

Antibodies, Monoclonal↗
PubMed1998

Antibodies to varicella zoster virus in the cerebrospinal fluid of neonates with seizures.

Four neonates with convulsions had IgG antibodies in their cerebrospinal fluid (CSF) to varicella zoster virus (VZV). These antibodies were found in the sera of two of these patients after the age of 6 months. Antibodies to 16 different microbes were studied from the serum and CSF of 201 neonates with neurological problems. The presence of DNA specific to HSV-1, HSV-2, and VZV in the CSF was also investigated using the polymerase chain reaction (PCR). Antibodies to VZV were detected in the CSF of four neonates. Antibody indices suggested production of VZV specific antibodies in the central nervous system. These findings suggest that intrathecal production of antibodies to VZV can appear in neonates with neurological problems, which suggests that intrauterine VZV infection can be acquired without cutaneous symptoms in the mother.

Antibodies, Viral↗
PubMed1997

Spatial orientation of tissue-type plasminogen activator bound at the melanoma cell surface.

Human melanoma cells produce tissue-type plasminogen activator (tPA) which is bound to the cell surface where it effectively mediates generation of plasmin. The present study is focused on analysis of involvement of the tPA domains in binding of the enzyme to the cell surface. The extent of plasminogen activation by tPA of melanoma cells was measured using an immunocapture assay. The activator anchored to solid surface via monoclonal antibodies directed to the individual domains of the activator exhibited variable enzymatic activity. The tPA was the most effective when bound by the antibodies against kringle-1 or kringle-2. Accessibility of the epitopes within cell surface-bound tPA was probed by the same set of monoclonal antibodies. FACS analysis showed that the epitopes within the finger/growth factor domain one part of the kringle-2 domain and the active site epitope were the most exposed. The kringle-1 domain epitope and the protease region epitope appeared partially exposed. Full-length melanoma-derived tPA and three recombinant domain-deletion variants of tPA were compared for their capacity to bind to the melanoma cells. The estimated IC50 value for the melanoma-derived tPA was 2.3 +/- 0.25 microM. Comparable IC50 values were found for the tPA variant lacking the finger domain (3.6 +/- 0.6 microM) as well as for the variants consisting only of the kringle-2 and protease domains (7.5 +/- 0.45 microM). In contrast the value found for a tPA variant lacking the kringle-2 domain was > 100 microM. The consistent results obtained by the three different experimental approaches provide evidence that tPA binds to melanoma cells via its kringle-2 domain but binding sites within kringle-1 domain and protease domain may support the interaction. The finger domain did not contribute to the binding.

Antibodies, Monoclonal↗
PubMed1997

Plasminogen activator inhibitor-1 in neointima of vein grafts: its role in reduced fibrinolytic potential and graft failure.

BACKGROUND: Intimal smooth muscle cell proliferation is an underlying pathogenetic mechanism for neointimal hyperplasia and consequent vein graft failure. This study characterizes the expression of tissue-type plasminogen activator (TPA), urokinase-type plasminogen activator (UPA), and plasminogen activator inhibitor-1 (PAI-1) in hyperplastic vein grafts and normal venous tissue. METHODS AND RESULTS: Failing graft and control vein specimens from 14 donors were homogenized, and TPA and PAI-1 were quantified with ELISA. The amount of PAI-1 was seven times higher (4.2+/-2.1 versus 0.6+/-0.6 ng/mg protein, P<.005), but the TPA antigen content was markedly lower (3.1+/-2.1 versus 8.1+/-3.7 ng/mg protein, P<.005) in the stenosed grafts compared with the control veins. Strong immunohistochemical PAI-1 reactivity and in situ hybridization signals for PAI-1 and UPA mRNA were associated with the smooth muscle cells of the thickened intima of the grafts. Functional assays of the graft specimens showed an increased UPA/TPA ratio and a decreased total fibrinolytic activity in comparison with normal veins. CONCLUSIONS: Upregulation of PAI-1 mRNA expression and markedly increased amounts of PAI-1 antigen were detected in the vein grafts after the development of neointima. Furthermore, augmented UPA activity was found in the graft wall, but TPA was clearly depleted. Altogether, our findings imply decreased fibrinolytic potential in the stenosed graft, which may contribute to the graft occlusion.

Fibrin↗