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Biomedical subjects

J Blom

Publications and source records attributed to J Blom.

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

Lautropia mirabilis gen. nov., sp. nov., a gram-negative motile coccus with unusual morphology isolated from the human mouth.

An organism that seems to be identical to Orskov's 'Sarcina mirabilis' [Orskov, J. (1930) Acta Pathol Microbiol Scand Suppl III, 519-541] has been rediscovered in specimens from the upper respiratory tract of humans. Six strains were studied, and the results, which conformed to Orskov's description of S. mirabilis, were as follows. Rough to smooth colonies grow on many plated media and show extremely polymorphic cell morphology with round cells with diameters from 1 to > 10 microns. The smallest cells were often motile with circular movements. Strains were Gram-negative, facultatively anaerobic, oxidase and urease positive, and weakly catalase positive. Nitrate and nitrite were reduced, and glucose, fructose, sucrose and mannitol were fermented. Polysaccharide was produced on sucrose agar. Electron microscopy showed coccoid cells with a bundle of three to nine flagella, a Gram-negative cell-wall morphology, and aggregates of irregular cells held together by a common surface layer. The mean mol% (G+C) of the organisms was 65.0. 16S-ribosomal RNA sequencing revealed that the organism belongs to the beta subgroup of Proteobacteria, separate from all other described genera, but most closely related to Burkholderia. The name Lautropia mirabilis is proposed for this organism.

Bacterial Typing Techniques↗
PubMed1994

Immunoelectron microscopy of antigens of Bordetella pertussis using monoclonal antibodies to agglutinogens 2 and 3, filamentous haemagglutinin, pertussis toxin, pertactin and adenylate cyclase toxin.

Immunogold electron microscopy and monoclonal antibodies (Mabs) were used to localize surface-related antigens of Bordetella pertussis. Unfixed organisms of B. pertussis strains which are included in the Danish whole-cell pertussis vaccine and fixed cells from a vial of vaccine were examined. Mabs to agglutinogens 2 and 3 labelled fimbria-like structures on both live and fixed cells in a serotype-specific manner. Mab against pertactin, a 69 kDa outer membrane protein, produced intense labelling of the surface of unfixed cells, whereas staining was reduced when fixed cells were examined. Mabs against filamentous haemagglutinin (FHA) stained aggregates of material between or adherent to both live and fixed cells. Negligible labelling of FHA on cell surfaces was observed. Mabs to pertussis toxin and adenylate cyclase toxin labelled loose-structured material which was adherent to or between cells, but neither of these toxin antigens was expressed on the surface of B. pertussis in Mab recognizable form. It is therefore suggested that these antigens are readily dispersed after exit from the outer membrane of B. pertussis.

Adenylate Cyclase Toxin↗
PubMed1994

Antiidiotypic antibodies mimic molecular and functional properties of human IL-1 beta in vitro and in vivo.

We obtained affinity-purified polyclonal anti-id antibodies against mAb MhC1 and BrhC3, which recognize amino acids 133-147 at the N-terminus of mature human IL-1 beta. mAb MhC1 and BrhC3 have been shown to inhibit binding of IL-1 beta to type I IL-1R, and to neutralize IL-1 beta bioactivity in a number of in vitro assays. We show that affinity-purified antibodies against the MhC1 and BrhC3 idiotypes specifically bind to type I IL-1 beta IL-1R and that this binding is inhibited by both IL-1 beta and IL-1ra; anti-id antibodies were also able to trigger IL-1R-dependent events, such as IL-8 secretion by human skin fibroblasts and pyrogenic effect after injection in mice. These anti-id antibodies, therefore, behave as structural and functional "images" of IL-1 beta, both in vivo and in vitro. These data indicate the idiotypic strategy as a powerful tool to study the fine specificity of receptor-ligand interactions. Moreover, this is, to our knowledge, the first report showing that the "internal image" of a cytokine can be active in vivo.

Animals↗
PubMed1994

Intracellular location of Mycoplasma genitalium in cultured Vero cells as demonstrated by electron microscopy.

The original two strains of Mycoplasma genitalium were isolated from the human urogenital tract. No other strains have been isolated from this site since then. We have recently succeeded in propagating a third strain from a urogenital specimen from a patient with urethritis in Vero cell cultures. By electron microscopy mycoplasmas were demonstrated intracellularly in about 10% of the examined Vero cells. Various stages of penetration into the cells could be observed. The flask-shaped organisms seemed to penetrate into the cells by the tip-end which included a rodlike structure. The intracellular location of normal mycoplasmas were in membrane-bound vacuoles very close to the nucleus, occasionally together with a few disintegrated organisms. In a few cells additional material was entangling the mycoplasmas in the cytoplasmic vacuoles. The potential for intracellular survival of M. genitalium may help the organism to evade the defence mechanisms of the human body. This trait may be considered a pathogenic property which supports the presumption that M. genitalium has clinical importance.

Animals↗
PubMed1993

Characterization of two human monoclonal antibodies reactive with HLA-B12 and HLA-B60, respectively, raised by in vitro secondary immunization of peripheral blood lymphocytes.

We have developed an in vitro immunization system for the production of B-cell lines that secrete HLA-specific human mAbs. For this purpose, peripheral blood lymphocytes of parous women were stimulated with pools of allogeneic lymphocytes. Preferential outgrowth of B-lymphocytes was effected by inclusion of rIL-2 and a B-cell specific nucleoside analogue. Stimulated B cells were immortalized by EBV transformation, and specific antibody-producing transformants were fused to heteromyeloma or mouse myeloma cell lines, yielding stable hybridomas. This approach has led to the successful development of two human heterohybridomas producing HLA-specific mAbs reactive by complement-mediated cytotoxicity. The specificities of these human mAbs, reactive with HLA-B12(44 + 45) and HLA-B60, respectively, are fully concordant with those of HLA-typing sera.

Animals↗
PubMed1993

A human monoclonal antibody, produced following in vitro immunization, recognizing an epitope shared by HLA-A2 subtypes and HLA-A28.

In vitro immunization and subsequent immortalization of peripheral blood cells of a multiparous woman has resulted in the production of a stable human mouse heterohybridoma, 5C2A2, secreting an HLA-A2/A28-specific human monoclonal antibody. Although possibly exposed to HLA-A2 by transfusions, the cell donor showed no HLA-A2-specific serum antibodies. The present protocol for in vitro immunization includes the elimination of suppressor cells from the responder cell population, the presence of irradiated allogeneic lymphocytes as a source of antigen, as well as stimuli--recombinant interleukin-2 and a B-cell specific nucleoside analogue--causing the proliferation of B lymphocytes, prior to immortalization. The ability of the antibody 5C2A2 to detect all known HLA-A2 subtypes, except A2.3, and A28, allows identification of the serological epitope on the HLA-A2 molecule. Application of this in vitro immunization method allows the production of a set of HLA monoclonal antibody-secreting human hybridomas, independent of the existence of serum HLA antibodies in the lymphocyte donors.

Amino Acid Sequence↗
PubMed1993

An ultrastructural study of HIV-infected human dendritic cells and monocytes/macrophages.

The ultrastructure of dendritic cells (DC) isolated from HIV-negative blood donors revealed three morphologically distinct cell types: type I had an irregularly shaped nucleus with a high content of heterochromatin and numerous short pseudopodia; type II possessed a smoother boundary, a "blast-like" nucleus and a few veil-like protrusions; and type III resembled veil-like cells (DC) in the lymph. HIV induced a productive virus infection in type II DC with budding of virus solely from the cell surface. HIV was observed in cytoplasmic vacuoles of type III DC, but no budding of virus was observed from these cells. HIV was not observed in type I DC. Isolated monocytes were cultured for 8-15 days in order for these cells to differentiate into macrophages. Cultured monocytes and macrophages became highly vacuolized when infected with HIV strains and productive virus infection was localized in intracytoplasmic vacuoles. Budding from the cell surface was rarely observed. When monocytes were co-cultured with CD4(+)-infected lymphocytes, specialized electron-dense contact zones were observed in monocyte-like cells. Virus particles were found outside some of these contact zones, indicating that the zones may play a role in the penetration and transfer of virus from cell to cell.

Antigens, CD↗
PubMed1993

Licochalcone A, a novel antiparasitic agent with potent activity against human pathogenic protozoan species of Leishmania.

Licochalcone A, an oxygenated chalcone isolated from the roots of Chinese licorice plant, inhibited the growth of both Leishmania major and Leishmania donovani promastigotes and amastigotes. The structure of the licochalcone A was established by mass and nuclear magnetic resonance spectroscopies and by synthesis, and its purity was verified by high-pressure liquid chromatography. The 50% inhibition of growth of logarithmic- and stationary-phase promastigotes of L. major, as measured by [3H]thymidine uptake, were 4 and 2.5 micrograms/ml, respectively. The growth of L. major promastigotes was totally inhibited after a 20-h incubation period with licochalcone A at 5 micrograms/ml. At a concentration of 0.5 microgram/ml, licochalcone A markedly reduced the infection rate of human peripheral blood monocyte-derived macrophages and U937 cells with L. major promastigotes and exhibited a strong intracellular killing of the parasite. These data show that intracellular Leishmania amastigotes are more susceptible than promastigotes to licochalcone A. Results of studies on the site of action of licochalcone A indicate that the target organelle appears to be the parasite mitochondria. These findings demonstrate that licochalcone A in concentrations that are nontoxic to host cells exhibits a strong antileishmanial activity and that appropriate substituted chalcones might be a new class of antileishmanial drugs.

Animals↗
PubMed1993

The essential yeast protein MIM44 (encoded by MPI1) is involved in an early step of preprotein translocation across the mitochondrial inner membrane.

The essential yeast gene MPI1 encodes a mitochondrial membrane protein that is possibly involved in protein import into the organelle (A. C. Maarse, J. Blom, L. A. Grivell, and M. Meijer, EMBO J. 11:3619-3628, 1992). For this report, we determined the submitochondrial location of the MPI1 gene product and investigated whether it plays a direct role in the translocation of preproteins. By fractionation of mitochondria, the mature protein of 44 kDa was localized to the mitochondrial inner membrane and therefore termed MIM44. Import of the precursor of MIM44 required a membrane potential across the inner membrane and involved proteolytic processing of the precursor. A preprotein in transit across the mitochondrial membranes was cross-linked to MIM44, whereas preproteins arrested on the mitochondrial surface or fully imported proteins were not cross-linked. When preproteins were arrested at two distinct stages of translocation across the inner membrane, only preproteins at an early stage of translocation could be cross-linked to MIM44. Moreover, solubilized MIM44 was found to interact with in vitro-synthesized preproteins. We conclude that MIM44 is a component of the mitochondrial inner membrane import machinery and interacts with preproteins in an early step of translocation.

Fungal Proteins↗
PubMed1993

First cases of microsporidiosis in Scandinavian patients with AIDS.

The first 2 cases of infection with Enterocytozoon bieneusi in Denmark and Scandinavia are reported. Both patients were women and to the best of our knowledge this is the first report of E. bieneusi in female AIDS patients. Both had late stage AIDS, and both had complained of intermittent diarrhoea for more than 1 year. At the time microsporidiosis was diagnosed, no other pathogens causing diarrhoea were found. Immunodeficient patients with chronic unexplained diarrhoea should be investigated for intestinal microsporidiosis, especially as treatment is now available.

AIDS-Related Opportunistic Infections↗
PubMed1993

Survival and ultrastructural changes of Helicobacter pylori after phagocytosis by human polymorphonuclear leukocytes and monocytes.

Few studies have been carried out on the phagocytosis and killing of Helicobacter pylori by both polymorphonuclear leukocytes (PMNs) and monocytes. In this study, H. pylori was incubated for up to 60 min either alone or with phagocytes in the presence or absence of human serum. Both non-immune serum and immune serum were used. Reduction in the number of H. pylori, which corresponds to the killing of H. pylori, was analysed by a colony count and ultrastructural changes were studied by electron microscopy. No reduction in the number of H. pylori was found when the bacteria were incubated alone or with phagocytes in the absence of serum. It is remarkable that unopsonized H. pylori was phagocytosed. When immune serum was added to the suspensions of bacteria and phagocytes, the killing rate of H. pylori was found to depend on the ratio of H. pylori to phagocytes. Thus an excess of monocytes reduced the number of H. pylori, whereas an excess of PMNs resulted in complete killing of H. pylori. On incubation with PMNs and serum, ultrastructural changes were observed in the majority of the bacteria whether they were phagocytosed or not. Controls without serum did not show any changes in the morphology of H. pylori, indicating that components in the serum play an important role in the phagocytosis and killing of H. pylori. In contrast, several of the phagocytosed bacteria were found to be unaffected after incubation with monocytes and serum. Such preparations often contained large aggregates of platelets surrounding unaffected H. pylori. In the gastric mucosa, H. pylori is often found in excess as compared to the phagocytes. If these results can be compared to the situation in vivo, the phagocytes seem to be ineffective in the killing of H. pylori, and other immune mechanisms may therefore be of importance for the elimination of H. pylori from the gastric epithelium. The possible intracellular survival of H. pylori should be taken into account when treatment regimes for H. pylori infections are chosen.

Helicobacter pylori↗
PubMed1992

MPI1, an essential gene encoding a mitochondrial membrane protein, is possibly involved in protein import into yeast mitochondria.

To identify components of the mitochondrial protein import pathway in yeast, we have adopted a positive selection procedure for isolating mutants disturbed in protein import. We have cloned and sequenced a gene, termed MPI1, that can rescue the genetic defect of one group of these mutants. MPI1 encodes a hydrophilic 48.8 kDa protein that is essential for cell viability. Mpi1p is a low abundance and constitutively expressed mitochondrial protein. Mpi1p is synthesized with a characteristic mitochondrial targeting sequence at its amino-terminus, which is most probably proteolytically removed during import. It is a membrane protein, oriented with its carboxy-terminus facing the intermembrane space. In cells depleted of Mpi1p activity, import of the precursor proteins that we tested thus far, is arrested. We speculate that the Mpi1 protein is a component of a proteinaceous import channel for translocation of precursor proteins across the mitochondrial inner membrane.

Amino Acid Sequence↗
PubMed1992

Capsular polysaccharide is linked to the outer surface of type 6A pneumococcal cell walls.

The in situ attachment of capsular polysaccharide of type 6A pneumococci was examined by immunoelectron microscopy using anti-type 6A monoclonal antibody. The result discloses an asymmetrical cross-section of pneumococcal cell walls because capsular polysaccharides are located on the outer surface of the walls only, in contrast to the cell wall polysaccharide, which has been shown to be located on both surfaces.

Antibodies, Monoclonal↗
PubMed1992

Histopathological changes in exocrine glands of murine transplantation chimeras. I: The development of Sjögren's syndrome-like changes secondary to GVH induced lupus syndrome.

Sjögren's syndrome (SS) is a connective tissue disease characterized by general affection of exocrine glands. The three main components of SS are: dry eyes, dry mouth, and other connective tissue disease. When only two of these, dry eyes and dry mouth, are present, the disease is designated primary SS. In the presence of the third component, most commonly SLE or RA, with one or both of the two first components the disease is designated secondary SS. In murine transplantation chimeras, we have demonstrated the development of both primary and secondary SS depending upon the mouse strains used. We transferred large numbers of viable leucocytes from homozygotic donors to heterozygotic recipients. When DBA/2 mice were used as donors, a full-developed SLE-syndrome, with autoantibodies against native DNA, nuclear antigens, and red blood cells was observed. We found immune deposits in skin ("lupus band") and kidneys, immune complex glomerulonephritis (ICGN), proteinuria, ascites, and hepatosplenomegaly. In later stages, we found a generalized dacryoadenitis. In the kidneys we found interstitial nephritis, and occasionally "half-moon" nephritis. In skin, immune deposits were demonstrated in intercellular spaces. These findings are similar to those found in patients with Sjögren's syndrome secondary to SLE. The murine transplantation chimera is therefore an experimental model for spontaneous autoimmune diseases.

Animals↗
PubMed1991

Fatal septicaemia with Selenomonas sputigena and Acinetobacter calcoaceticus. A case report.

A 38-year-old man with a history of alcohol abuse developed rapidly fulminating septicaemia and died. Selenomonas sputigena and Acinetobacter calcoaceticus were isolated from a blood culture. Selenomonas sputigena is a motile anaerobic gram-negative rod rarely associated with systemic disease. Difficulties in isolation and taxonomic identification are discussed.

Acinetobacter↗
PubMed1990

A 40 kd protein binds specifically to the 5'-untranslated regions of yeast mitochondrial mRNAs.

Using a gel mobility shift assay we show that a 40 kd protein (p40), present in extracts of yeast mitochondria, binds specifically to the 5'-untranslated leader of cytochrome c oxidase subunit II mRNA. Binding of p40 to coxII RNA protects an 8-10 nucleotide segment from diethylpyocarbonate modification, indicating that the protein interacts with only a restricted region of the 5'-leader. This segment is located at position -12 with respect to the initiation AUG. Deletion of 10 nucleotides encompassing this site completely abolishes protein binding. Nevertheless, Bal31 deletion analysis within the coxII leader shows that a major part of the leader is essential for p40 binding, suggesting that binding of the protein is also dependent on secondary structural features. p40 binds to other mitochondrial leader mRNAs including those for coxI, coxIII and cyt b. p40 is present in a cytoplasmic (rho0) petite mutant lacking mitochondrial protein synthesis. It is therefore presumably nuclear encoded. The possible biological function of the protein is discussed.

Base Sequence↗