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Biomedical subjects

H Janssen

Publications and source records attributed to H Janssen.

At least 73 records · Page 4Linked to original sources
PubMed1991

Assembly and routing of von Willebrand factor variants: the requirements for disulfide-linked dimerization reside within the carboxy-terminal 151 amino acids.

The precursor protein of von Willebrand factor (pro-vWF) consists of four different repeated domains, denoted D1-D2-D'-D3-A1-A2-A3-D4-B1-B2-B3-C1-C2, followed by a carboxy-terminal region of 151 amino acids without obvious internal homology. Previously, we have shown the requirement of the domains D1, D2, D', and D3 of pro-vWF in the assembly of pro-vWF dimers into multimers. Here, we define the domains of vWF involved in dimerization, using deletion mutants of full-length vWF cDNA transiently expressed in monkey kidney COS-1 cells. It is shown that only the carboxy-terminal 151 amino acid residues of vWF are required for dimerization. In addition, by analyzing a construct, encoding only the carboxy-terminal 151 amino acids of vWF, we find that the formation of dimers is an event independent of other domains present on pro-vWF, such as the domains C1 and C2 previously suggested to be involved in dimerization. Furthermore, it is shown that a deletion mutant of vWF, lacking the carboxy-terminal 151 amino acid residues and thus unable to dimerize, is proteolytically degraded in the ER. In contrast, a mutant protein, composed only of the carboxy-terminal 151 amino acids of vWF, and able to dimerize, is transported from the ER in a similar fashion as wild-type vWF. The role of the ER in the assembly of vWF is discussed with regard to the data presented in this paper on the intracellular fate of several vWF mutant proteins.

Animals↗
PubMed1991

Integrin alpha 6/beta 4 complex is located in hemidesmosomes, suggesting a major role in epidermal cell-basement membrane adhesion.

The alpha 6/beta 4 complex is a member of the integrin family of adhesion receptors. It is found on a variety of epithelial cell types, but is most strongly expressed on stratified squamous epithelia. Fluorescent antibody staining of human epidermis suggests that the beta 4 subunit is strongly localized to the basal region showing a similar distribution to that of the 230-kD bullous pemphigoid antigen. The alpha 6 subunit is also strongly localized to the basal region but in addition is present over the entire surfaces of basal cells and some cells in the immediate suprabasal region. By contrast staining for beta 1, alpha 2, and alpha 3 subunits was very weak basally, but strong on all other surfaces of basal epidermal cells. These results suggest that different integrin complexes play differing roles in cell-cell and cell-matrix adhesion in the epidermis. Immunoelectron microscopy showed that the alpha 6/beta 4 complex at the basal epidermal surface is strongly localized to hemidesmosomes. This result provides the first well-characterized monoclonal antibody markers for hemidesmosomes and suggests that the alpha 6/beta 4 complex plays a major role in epidermal cell-basement membrane adhesion. We suggest that the cytoplasmic domains of these transmembrane glycoproteins may contribute to the structure of hemidesmosomal plaques. Immunoultrastructural localization of the BP antigen suggests that it may be involved in bridging between hemidesmosomal plaques and keratin intermediate filaments of the cytoskeleton.

Animals↗
PubMed1990

[Grief work an support experienced during abortion and stillbirth].

We investigated by means of a semi-structured, oral interview how women cope with a miscarriage or stillbirth. The need for psychosocial support and the support which was experienced were also studied. The results stress that the mourning process after a miscarriage or stillbirth proceeds in one sense like the 'conventional' mourning process, but differs in some aspects. Women with one or more children show less intense emotions than childless women. The experiences with the professional help and the environmental support differ depending on the moment: before, during or after the bereavement. Negative experiences usually refer to a too businesslike attitude of doctors and nurses in charge, lack of information, shortcomings in the aftercare, clumsy reactions of the environment and unfulfilled needs for contact with other women who had a miscarriage or stillbirth.

Abortion, Spontaneous↗
PubMed1990

Receptors for tumor necrosis factor on neoplastic B cells from chronic lymphocytic leukemia are expressed in vitro but not in vivo.

Recombinant tumor necrosis factor-alpha (TNF-alpha) is a cytokine that induces proliferation of neoplastic B cells from patients with chronic lymphocytic leukemia (CLL). To gain insight into the mechanisms involved in regulating TNF responsiveness, we have examined TNF receptor expression on neoplastic B-CLL cells. We have demonstrated that freshly isolated neoplastic B cells from patients with CLL did not express TNF receptors. After 1 day of incubation in culture medium, TNF receptors were detectable in the range of 540 to 1,500/cell. Kinetic experiments revealed that receptor expression was half-maximal after 3 hours of culturing and required de novo protein synthesis. The Scatchard plots of TNF-alpha binding indicated a single set of high-affinity TNF receptors with a dissociation constant of 70 pmol/L. TNF receptor expression in vitro was found in all examined cases. All cytokines tested, with the exception of IL-2, did not influence the expression of TNF receptors. The TNF receptor expression is enhanced in B-CLL cells cultured in the presence of interleukin-2 when compared with the receptor expression of cells cultured in medium alone. Our data suggest that neoplastic B-CLL cells in patients with stable disease do not express TNF receptors in vivo and that an unknown mechanism suppressing TNF receptor expression in vivo may play a role in growth regulation of neoplastic B cells.

B-Lymphocytes↗
PubMed1990

In situ localization by double-labeling immunoelectron microscopy of anti-neutrophil cytoplasmic autoantibodies in neutrophils and monocytes.

Anti-neutrophil cytoplasmic autoantibodies (ANCA) associated with active Wegener's granulomatosis are directed against a soluble 29-Kd protein present in human neutrophils and monocytes. Affinity labeling with tritiated diisopropylfluorophosphate (3H-DFP) suggested that ANCA-antigen is a serine protease. We used immunoelectron microscopy to study the in situ localization of the ANCA-antigen in normal human neutrophils and monocytes using immunoglobulin G (IgG) from ANCA-positive patients and a mouse monoclonal antibody against the ANCA-antigen. Label was observed on the large granules of the neutrophils and in granules of monocytes. Double-labeling, using anti-myeloperoxidase or the peroxidase reaction as markers for azurophil granules and anti-lactoferrin as marker for specific granules, showed that ANCA is colocalized with markers of azurophil granules but not with lactoferrin. Furthermore, elastase and cathepsin G were found in the azurophil granules of neutrophils and in the peroxidase-positive granules of monocytes, colocalized with ANCA-antigen. Cytochalasin-B-treated neutrophils stimulated with N-formyl-methionyl-leucyl-phenylalanine (fMLP) formed large intracellular vacuoles and were partially degranulated. Some vacuoles contained ANCA-antigen, as well as myeloperoxidase, elastase, and cathepsin G, demonstrating release of these enzymes from the azurophil granules into vacuoles. Our results demonstrate that ANCA-antigen is located in myeloperoxidase-containing granules of neutrophils and monocytes, and is packaged in the same granules as elastase and cathepsin G, the two previously identified serine proteases of myeloid leukocytes.

Autoantibodies↗
PubMed1990

Serum CK-BB activity in the preterm infant and outcome at two and four years of age.

The relationship between serum creatine kinase brain-specific isoenzyme (CK-BB) activity immediately after birth and neurodevelopmental outcome at two and four years corrected age was studied prospectively in 45 preterm infants (less than 34 weeks gestation). Nine infants died during the neonatal period and one was lost to follow-up. Of the 35 children available for follow-up, seven had motor disabilities: four severe diplegia, two mild to moderate diplegia and one hemiplegia. No relationship existed between these motor disabilities and serum CK-BB activity after birth. There seemed to be a relationship between increased serum CK-BB after birth and low scores on the Bayley Scales of Mental Development, but this did not reach statistical significance. At the age of four years, four of the five survivors with high serum CK-BB activity after birth (greater than 25U/L) needed special schooling because of mental retardation. Increased serum CK-BB activity after birth may be associated with delayed mental development, but further study is needed, especially of asphyxiated infants.

Brain Diseases↗
PubMed1989

Use of topical ketanserin in the treatment of skin ulcers: a double-blind study.

The use of a 2% ointment formulation of ketanserin, an S2-serotoninergic blocking agent, was investigated in a randomized double-blind clinical trial for its effect on the healing of wounds of patients with decubitus, venous, and ischemic skin ulcers. The result demonstrates a significant difference in favor of the ketanserin-treated group (35 patients) versus the placebo-treated group (37 patients) on the basis of two factors: formation of granulation tissue and epithelialization. In addition, a significant difference of 150% in the initial velocity of wound closure was observed in favor of the patients treated with ketanserin. This effect was persistent during the entire study period.

Administration, Cutaneous↗
PubMed1988

Endocytosis and intracellular routing of an antibody-ricin A chain conjugate.

An immunotoxin (IT) was prepared from monoclonal antibody (MoAb) 115D8 and ricin A chain. MoAb 115D8 is directed against the carcinoma-associated sialomucin MAM-6. In a protein synthesis inhibition assay this IT was cytotoxic for the human breast cancer cell line T47D. Using postembedding immunoelectron microscopy the binding and intracellular routing of the IT in T47D cells were studied by simultaneous labeling of both IT moieties, MoAb and A chain, and compared with the fate of native ricin and MoAb 115D8. The IT was internalized into the cell by two different pathways: one via coated pits-coated vesicles followed by transport to the lysosomes and one via large enclosed invaginations of the plasma membrane which apparently fused with lysosomes. This internalization was similar to the endocytosis of MoAb 115D8. During transport via both pathways the IT remained intact until it reached the lysosomes as suggested by the observation that the labels for 115D8 and ricin A chain remained closely associated. Moreover, in areas with abundant endocytic vesicles the labels for both IT moieties were also found in the cytosol, suggesting that intact IT is translocated from the vesicles into the cytosol. In control experiments, native ricin, but not unconjugated MoAb 115D8, was found in the cytosol after internalization. Data presented here show for the first time the complete intracellular pathway of an antibody-ricin A chain conjugate, including the translocation of the A toxin subunit into the cytosol. This IT may be useful for therapy of those tumors which express a high level of MAM-6 on the cell surface.

Antibodies, Monoclonal↗
PubMed1987

A complex of platelet glycoproteins Ic and IIa identified by a rat monoclonal antibody.

A rat monoclonal antibody, GoH3, recognizes cell surface antigens on epithelial cells in a variety of tissues in both man and mouse. Furthermore, the antibody showed reactivity with endothelial cells and blood platelets. The molecule recognized by GoH3 on platelets was determined by immunoprecipitation, followed by analysis on one- and two-dimensional sodium dodecyl sulfate-polyacrylamide gels. GoH3 precipitated glycoproteins Ic and IIa from both human and mouse platelets. Glycoprotein Ic consists of disulfide-linked heavy and light chains which both appeared to be glycosylated. As determined by enzymatic digestion followed by gel analyses, both "complex" and "high mannose" type of N-linked oligosaccharides are present on the heavy and light chain of human glycoprotein Ic and on the heavy chain of mouse glycoprotein Ic. The light chain of mouse glycoprotein Ic only carries high mannose type of N-linked oligosaccharides. The N-linked glycans on human and mouse glycoprotein IIa are all of the complex type. The glycoproteins Ic and IIa co-sedimented in sucrose gradients and formed complexes upon treatment of intact platelets with the chemical cross-linking reagent dithiobis(succinimidyl propionate). Dissociation of the complex by chaotropic agents followed by immunoprecipitation establishes that the epitope recognized by GoH3 is located on the Ic molecule. These results provide evidence that the two glycoproteins, Ic and IIa, exist as a heterodimer complex in the platelet membrane.

Animals↗
PubMed1986

Mouse monoclonal antibodies direct phagocytosis of tumor cells by human monocytes.

Human peripheral blood monocytes were found to be capable of phagocytizing human B-non Hodgkin's lymphoma (NHL) cells coated with mouse monoclonal antibodies (MoAbs). The MoAbs used recognized idiotypic determinants on the surface immunoglobulin (Ig) of the tumor cells. MoAbs of IgG1 and IgG2a subclass were equally effective in inducing phagocytosis. Preincubation of the monocytes with heat aggregated Ig from human or mouse serum inhibited phagocytosis to the same degree, suggesting involvement of an Fc receptor on the monocytes that binds both human and mouse antibodies.

Animals↗
PubMed1985

Biochemical characterization and cellular localization of a formalin-resistant melanoma-associated antigen reacting with monoclonal antibody NKI/C-3.

A monoclonal antibody (MAb NKI/C-3) produced against a purified membrane preparation of human melanoma cells reacts preferentially with sections of formaldehyde-fixed and paraffin-embedded tissues of melanoma, nevocellular nevi, carcinoids and medullary carcinomas of the thyroid. NKI/C-3 did not react with basal-cell carcinoma, brain tissue or brain tumors, and in only 14/196 other tumors was a clear cross-reactivity observed, e.g. with prostate carcinomas and a minority of primary breast, ovarian, lung and clear-cell carcinomas. This antibody was used in an immuno-electron microscopic study for the cellular localization of the antigen. The antigen was dispersed in the cytoplasm of melanoma cells, and more concentrated inside vacuoles and sometimes also on the melanosomes. Occasionally, the antigen was seen on the cell surface. The nature of the antigen was determined in an enzyme immunoassay (EIA). It was found that the antigen is a glycoprotein with a disulfide-dependent configuration that is essential for recognition by the MAb. The antigen was distributed heterogeneously during gel filtration as well as during SDS-polyacrylamide gel electrophoresis in the region of 25-110 kd proteins. A purified antigen preparation that was obtained after affinity chromatography on a column of MAb NKI/C-3 linked to Sepharose 4B contained a carbohydrate:protein ratio of 1:3.5.

Animals↗
PubMed1984

Complete nucleotide sequence of tobacco streak virus RNA 3.

Double-stranded cDNA of in vitro polyadenylated tobacco streak virus (TSV) RNA 3 has been cloned and sequenced. The complete primary structure of 2,205 nucleotides reveals two open reading frames flanked by a leader sequence of 210 bases, an intercistronic region of 123 nucleotides and a 3'-extracistronic sequence of 288 nucleotides. The 5'-terminal open reading frame codes for a Mr 31,742 protein, which probably corresponds to the only in vitro translation product of TSV RNA 3. The 3'-terminal coding region predicts a Mr 26,346 protein, probably the viral coat protein, which is the translation product of the subgenomic messenger, RNA 4. Although the coat proteins of alfalfa mosaic virus (A1MV) and TSV are functionally equivalent in activating their own and each others genomes, no homology between the primary structures of those two proteins is detectable.

Amino Acid Sequence↗
PubMed1984

Binding of lectins to human mammary tumors: ultrastructural study.

The site of several lectin receptors in human mammary tumors and stroma was studied with the electron microscope. The advantage of the ultrastructural over light microscopic study was that lectin receptors could be localized with precision on the different cell types of the tumor and stroma. Eighteen human mammary carcinomas were incubated with three peroxidase-labeled lectins: peanut agglutinin (PNA), Helix pomatia, and Ulex europaeus I (UEA). These lectins reacted in a selective way; some tumors were negative and others showed reaction in some areas of the tumor and/or the stroma. No correlation was found, however, between the presence of these lectin receptors on the tumor cells and either hormone receptors or histological type of the tumors. These results show that the value of the presence of lectin receptors in human mammary tumors as markers for evaluation of mammary lesions is more complex than thought up to now. The most relevant observations on the stroma cells and inflammatory infiltrates were: (A) Some lymphocytes were positive with PNA, probably representing sessile T cells. In two carcinomas, abundant plasma cells were present in the infiltrates, always with PNA receptors. (B) In all mammary tumors where blood vessels were present in the sections, these were always stained with UEA. This supports the use of UEA as a marker for human endothelial cells even in pathologically altered tissues.

Breast Neoplasms↗
PubMed1983

Specific selection of host cell glycoproteins during assembly of murine leukaemia virus and vesicular stomatitis virus: presence of Thy-1 glycoprotein and absence of H-2, Pgp-1 and T-200 glycoproteins on the envelopes of these virus particles.

Using the indirect immunoelectron microscopy technique, it was investigated whether during assembly of murine leukaemia virus (MuLV) and vesicular stomatitis virus (VSV), the glycoproteins (gp) Thy-1, H-2, Pgp-1 and T-200 present on the surface of BW5147 and BuEL4 leukaemia cell lines were incorporated into the virus envelopes. This work was done mainly with monoclonal antibodies against these gps to exclude the presence of antibodies against endogenous MuLV present in conventional mouse antisera. Thy-1 gps were incorporated into MuLV and VSV envelopes. In contrast, H-2, Pgp-1 and T-200 gps were excluded from the budding of both virus particles. To study whether the presence of Thy-1 gps on the viral envelopes is due to some lateral affinity of this molecule with viral gps, the physical association of Thy-1.1 antigens and MuLV antigens was studied with antibody-induced redistribution of both antigens on the BW5147 cell surface. Antibody-induced patching of the viral antigens did not result in co-patching of the Thy-1.1 antigens. In the reciprocal tests no co-redistribution of viral antigens with Thy-1.1 antigens was seen. These studies show that the presence of Thy-1.1 gp on the MuLV envelope cannot be due to a lateral affinity of this molecule with viral gps and that a selection of surface gps takes place during assembly of MuLV and VSV.

Animals↗
PubMed1981

Independence of H-2 and viral antigens on the cell surface and absence of H-2 antigens on murine leukemia virus and mouse mammary tumor virus particles.

By indirect immunoelectron microscopy we tested for the presence of H-2 antigens on murine mammary tumor virus (MMTV) and murine leukemia virus (MuLV) particles. The association of H-2 antigens and viral antigens on the virus-infected cell surface was investigated with antibody-induced redistribution. Mammary tumor cells and leukemia cell lines with different H-2 genotypes and carrying different MuMTV or MuLV were used. No H-2 antigens could be demonstrated on the envelope of MMTV and MuLV particles, even after the permeabilization of their envelopes with saponin. On the surface of virus-infected cells antibody-induced patching or capping of the viral antigens did not result in copatching or cocapping of the H-2 antigens. In the reciprocal tests no co-redistribution of viral antigens with H-2 antigens was seen. Our experiments failed to show any physical association between H-2 antigens and MMTV or MuLV antigens on the cell surface.

Animals↗
PubMed1981

Morphological study of virus-like particles in two transplantable tumours from BDX rats.

Virus-like particles were found in two transplantable tumours, Sp56 and Sp6, from BDX rats. Sp56, a neurogenic sarcoma, contains abundant C-type particles in all stadia nof morphogeneis. This tumour reacts with anti-Friend leukaemia virus gp70 and anti-Rauscher leukaemia virus p30 sera. Sp6, a fibrosarcoma, has abundant virus-like particles in the cytoplasm, very often associated with centrioles or basal bodies of a cilium. These particles consist of two concentric shells with a diam. of 60 to 65 nm. Released particles were found outside the cell with a diam. of 85 to 100 nm characterized by an envelope and an eccentrically located electron-dense nucleoid, surrounded by an intermediate layer. These virus-like particles show no cross-reaction with antisera against murine C- or B-type particles, but show ultrastructural similarity with virus particles recently described in Chinese hamster cells and in mouse cell lines infected with two retrovirus isolates from South-East Asian mice.

Animals↗