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Biomedical subjects

H Janssen

Publications and source records attributed to H Janssen.

At least 55 records · Page 3Linked to original sources
PubMed1997

Ultrastructural localization of Charcot-Leyden crystal protein in human eosinophils and basophils.

The Charcot-Leyden crystal (CLC) protein with lysophospholipase activity and carbohydrate-binding properties is a characteristic constituent of eosinophils and basophils. We investigated its subcellular distribution using immunoelectron microscopy. Eosinophil progenitors, mature eosinophils and basophils all contained CLC protein in their cytosol and in the euchromatin of the nucleus. A minor population of granules in eosinophils, increasing in number with maturation, and a more abundant granule-population in basophils, were found to contain CLC protein. Double-labeling experiments showed, in eosinophils, that CLC protein-containing granules contain also eosinophil peroxidase, a characteristic specific granule protein. This suggests a relationship between the CLC protein-containing organelle and the specific granule. In basophils both the CLC protein positive and the negative granules showed the same characteristic particulate-like structure of the granular matrix and both share the same membrane marker CD63. In nasal polyps, macrophages were observed phagocytosing necrotic eosinophils. In these macrophages CLC protein-containing vesicles were observed, probably representing late endosomes. The dual (cytosolic/nuclear and granular) localization of CLC protein suggests that this protein enters both a secretory and a nonsecretory pathway during its biosynthesis, indicating functional roles for this protein both within the cell and extracellularly.

Basophils↗
PubMed1997

Localization of granule proteins in human eosinophil bone marrow progenitors.

Eosinophils have a characteristic content of cationic proteins, stored in core-containing specific granules and released at sites of inflammation; coreless granules (sometimes called primary) are present in eosinophil promyelocytes. In order to determine a possible relationship between the two granule subsets, immunoelectron-microscopic techniques were used to determine the presence and precise intragranular distribution of major basic protein (MBP), eosinophil cationic protein (ECP), eosinophil peroxidase (EPO), and arylsulfatase B of eosinophil granules, as well as the Charcot-Leyden crystal (CLC) protein, in eosinophil progenitors of the bone marrow. MBP, ECP, EPO, and arylsulfatase B were observed in both coreless and core-containing (specific) granules. The difference in the distribution of MBP, having a uniform distribution in coreless granules and a crystalloid distribution in core-containing (specific) granules, could indicate a maturational process of a common organelle. CLC protein was distributed in the cytosol, in the euchromatin of the nuclei, but was also present in a rare granular compartment of both immature and mature eosinophils. The present findings suggest that coreless granules develop into core-containing specific granules.

Blood Proteins↗
PubMed1996

Subcellular localization of transforming growth factor-alpha in human eosinophil granulocytes.

Eosinophils are involved in the inflammatory response seen in allergy and helminthic infestations. Eosinophils synthesize transforming growth factor-alpha (TGF-alpha), which may play a role in the development of the characteristic fibrosis seen in longstanding high eosinophilia. Using immunoelectron microscopic techniques, eosinophils from peripheral blood of healthy individuals and from one patient with high eosinophilia showed presence TGF-alpha in matrix of the specific crystalloid-containing granules. In cryosections, TGF-alpha was also visualized in a vesicular compartment of the cytoplasm. In double-labeling experiments, the TGF-alpha of this latter compartment did not colocalize with CD63, a marker for lysosomes, nor with albumin of secretory vesicles. In extracts from eosinophils, obtained from healthy donors, immunoreactive TGF-alpha could be detected by enzyme-linked immunosorbent assay-technique. In addition, sera from two patients with high eosinophilia showed TGF-alpha concentrations of 1.5 ng/mL and 164 pg/mL, respectively, whereas TGF-alpha could not be detected in serum from healthy controls. In conclusion, TGF-alpha is present in the specific granules, and in an additional vesicular compartment of the cytoplasm of eosinophils.

Cryoultramicrotomy↗
PubMed1996

Direct vesicular transport of MHC class II molecules from lysosomal structures to the cell surface.

Newly synthesized MHC class II molecules are sorted to lysosomal structures where peptide loading can occur. Beyond this point in biosynthesis, no MHC class II molecules have been detected at locations other than the cell surface. We studied this step in intracellular transport by visualizing MHC class II molecules in living cells. For this purpose we stably expressed a modified HLA-DR1 beta chain with the Green Fluorescent Protein (GFP) coupled to its cytoplasmic tail (beta-GFP) in class II-expressing Mel JuSo cells. This modification of the class II beta chain does not affect assembly, intracellular distribution, and peptide loading of the MHC class II complex. Transport of the class II/ beta-GFP chimera was studied in living cells at 37 degrees C. We visualize rapid movement of acidic class II/beta-GFP containing vesicles from lysosomal compartments to the plasma membrane and show that fusion of these vesicles with the plasma membrane occurs. Furthermore, we show that this transport route does not intersect the earlier endosomal pathway.

Biological Transport↗
PubMed1996

Pregnancy following miscarriage: course of grief and some determining factors.

This prospective study aimed to investigate the impact of both (the speediness of) a subsequent pregnancy and the birth of a viable child on grief arising from a previous pregnancy loss. Data were collected from a series of written questionnaires. Of the 2140 pregnant women who participated in the study, 227 lost a baby by miscarriage (85%) or perinatal death (15%). In 221 women, the loss concerned a singleton. At each of four post-loss assessments, these women completed the Perinatal Grief Scale. They also indicated whether they had conceived again and, if they had, related how they felt about that. Data were analyzed by means of hierarchical multiple regression. Both conceiving again and the birth of a living child lessened grief. A speedy new pregnancy was only rarely found to be detrimental. It is suggested that parents, at least following miscarriage, no longer be advised to wait a specific time before conceiving again. Preferably their individual situation should be discussed with them in order to help them make their own informed decision concerning the subsequent pregnancy.

Abortion, Spontaneous↗
PubMed1994

Reconstitution of a surface transferrin binding complex in insect form Trypanosoma brucei.

In the bloodstream of the mammalian host, Trypanosoma brucei takes up host transferrin by means of a high-affinity uptake system, presumably a transferrin receptor. Transferrin-binding activity is seen in the flagellar pocket and is absent in insect form trypanosomes. By transfection we have reconstituted a transferrin-binding complex in insect form trypanosomes. Formation of this complex requires the products of two genes that are part of a variant surface glycoprotein expression site, expression site-associated gene (ESAG) 6 (encoding a protein with GPI-anchor) and ESAG 7 (encoding a protein without any obvious membrane attachment). This complex can be precipitated by transferrin-Sepharose and by an antibody directed only against the ESAG 6 protein. Transfection of ESAG 6 or 7 alone did not result in transferrin binding. In the transfected trypanosomes, the products of ESAG 6 alone and the combination of ESAG 6 and 7 did not exclusively localize to the flagellar pocket, but were present all over the surface of the trypanosome. The reconstituted transferrin-binding complex also did not result in the uptake of transferrin. Additional proteins present in bloodstream trypanosomes, but not in sufficient amounts in insect form trypanosomes, may therefore be required for the correct routing of the transferrin-binding complex to the flagellar pocket, and for its rapid internalization after ligand binding.

Amino Acid Sequence↗
PubMed1994

Cytokine-activated endothelial cells internalize E-selectin into a lysosomal compartment of vesiculotubular shape. A tubulin-driven process.

The fate of E-selectin expressed on TNF-activated monolayers of HUVEC was investigated by confocal laser scanning microscopy. Cytokine-activated endothelial cells internalized mAb to E-selectin in a very rapid, energy-dependent fashion. By contrast, mAb against ICAM-1 and VCAM-1 remained surface bound. The E-selectin mAb was recovered in intracellular compartments with a tubular morphology, some of which appeared to be interconnected. Cathepsin B, a ubiquitously expressed lysosomal protease, was found to co-localize in these structures. Functional specificity of E-selectin-internalization was observed upon addition of the fluorescent SLex-oligosaccharide to the activated HUVEC monolayers. Uptake into the same E-selectin-positive compartments was observed, whereas the control oligosaccharide Lex was not internalized at all. The process of internalization was found to be unaffected by most inhibitors of protein kinase C, cAMP-dependent PKA, or protein tyrosine kinase activity. Whereas cytochalasin B preincubation of HUVEC failed to inhibit the internalization process, colchicine and vinblastine, reagents that interfere with the metabolism of tubulin, prevented the formation of the elongated structures in which E-selectin would normally be internalized. Concomitantly, the expression of E-selectin at the cell surface was significantly increased.

Cell Adhesion Molecules↗
PubMed1994

Targeting major histocompatibility complex class II molecules to the cell surface by invariant chain allows antigen presentation upon recycling.

We studied the functional consequences of targeting class II molecules to either the cell surface or to endocytic structures by expressing HLA-DR1 in human kidney cells in the presence or absence of different forms of the invariant chain (Ii). Transfectants expressing class II molecules in the absence of Ii present influenza virus efficiently and co-expression of full length Ii does not further increase antigen presentation. Chimeric Ii containing the cytoplasmic domain of the transferrin receptor (Tfr-Ii) delivers class II molecules associated with Tfr-Ii to endosomal compartments, but this does not result in efficient antigen presentation. When class II molecules are targeted to the cell surface by Ii lacking either 15 (delta 15Ii) or 23 (delta 23Ii) amino acids from the cytoplasmic domain, a fraction of free class II molecules is also observed. Whereas delta 15Ii did not affect antigen presentation by class II molecules, delta 23Ii inhibited, but did not abrogate, the response. We show that class II molecules expressed in the presence of delta 23Ii can be internalized, followed by degradation of delta 23Ii and return of free class II alpha beta heterodimers to the cell surface. A fraction of the resulting free class II molecules is sodium dodecyl sulfate stable, indicating that internalization and reappearance of class II molecules at the cell surface can be an alternative route for antigen presentation. In all transfectants, class II molecules were found in endocytic compartments that labeled for CD63 and resembled the multilaminar MIIC compartments found in B cell lines. Ii is not required for endosomal targeting of class II molecules. The number of class II molecules observed in the multilaminar compartments correlates with the efficiency of antigen presentation.

Antigen Presentation↗
PubMed1994

Major histocompatibility complex class II molecules induce the formation of endocytic MIIC-like structures.

During biosynthesis, major histochompatibility complex class II molecules are transported to the cell surface through a late endocytic multilaminar structure with lysosomal characteristics. This structure did not resemble any of the previously described endosomal compartments and was termed MIIC. We show here that continuous protein synthesis is required for the maintenance of MIIC in B cells. Transfection of class II molecules in human embryonal kidney cells induces the formation of multilaminar endocytic structures that are morphologically analogous to MIIC in B cells. Two lysosomal proteins (CD63 and lamp-1), which are expressed in MIIC of B cells, are also present in the structures induced by expression of major histocompatibility complex class II molecules. Moreover, endocytosed HRP enters the induced structures defining them as endocytic compartments. Exchanging the transmembrane and cytoplasmic tail of the class II alpha and beta chains for that of HLA-B27 does not result in the induction of multilaminar structures, and the chimeric class II molecules are now located in multivesicular structures. This suggests that expression of class II molecules is sufficient to induce the formation of characteristic MIIC-like multilaminar structures.

Animals↗
PubMed1994

[Significance of coronary perfusion for therapeutic success in myocardial infarct].

Survival in acute myocardial infarction is dependent on several parameters. Some of them act by limiting the infarct size, others improve the prognosis independent of the final infarct size. Determinants of infarct size are time of vessel occlusion, degree of collaterals and area at risk. The latter two determinants do not offer a therapeutic approach in acute myocardial infarction. The most important therapeutic intervention remains the restoration of blood flow in the area at risk by either thrombolysis or PTCA. Reperfusion within 60 to 120 minutes significantly reduces mortality and infarct size. Within this time frame, changes in left ventricular function correlate with the survival rate. If reperfusion occurs later, the correlation between changes in left ventricular function and survival is poor or absent in some studies, despite a persistent survival benefit. After 4 bis 6 hours reperfusion is no longer able to limit infarct size significantly. However, this time frame is variable since there are wide variations in the degree of collaterals. With increasing occlusion time of the infarct related coronary artery, mechanisms independent of the limitation of infarct size will determine the prognosis. Late reperfusion has a beneficial effect on survival and on left ventricular function in certain cases. Left ventricular re-modeling and the incidence of severe ventricular arrhythmias can be reduced by delayed reperfusion. Reactivation of hibernating myocardium following reperfusion therapy may improve global left ventricular function. We analysed the importance of the infarct artery perfusion grade (TIMI flow) in 156 consecutive patients treated with infarct-PTCA. The most frequent indications for infarct-PTCA were failed thrombolysis and cardiogenic shock (Table 1).(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon, Coronary↗
PubMed1993

Evidence for small intracellular vesicles in human blood phagocytes containing cytochrome b558 and the adhesion molecule CD11b/CD18.

Human neutrophils contain a rapidly mobilizable pool of so-called secretory vesicles distinct from the azurophil granules and specific granules. Using human albumin as a marker for these intracellular vesicles in immuno-electron microscopy, we found that part of the cytochrome b558 in non-purified whole blood neutrophils colocalized in these vesicles. This was detected with monoclonal antibody (MoAb) CLB-48, binding to the high molecular weight subunit of cytochrome b558. Approximately 65% of the albumin-containing vesicles showed MoAb CLB-48 labeling. This was also found in eosinophilic granulocytes and in monocytes. Cytofluorimetric determination of cytochrome b558 expression on the plasma membrane of intact, nonpurified granulocytes (and monocytes) with MoAb 7D5, which is directed against an extracellular epitope of cytochrome b558, did not show any binding. However, granulocytes (and monocytes) significantly bound 7D5 after density centrifugation. The positive binding of 7D5 to purified neutrophilic granulocytes correlated with a strongly reduced labeling of cytochrome b558 in the albumin-positive vesicles. Binding of CD11b MoAb CLB-B2.12 to the alpha subunit of the complement receptor type 3 (CR3) on the surface of intact, nonpurified neutrophils was detected to a limited extent in whole blood samples, but was strongly increased upon density gradient centrifugation of the cells, as we have described before. Investigation at the ultrastructural level showed that the CD11b antigen codistributed with albumin in vesicular structures in nonpurified phagocytes, especially in neutrophils and eosinophils. Together, these data substantiate the idea of an intracellular store that can be easily mobilized (even under the simple stress condition of density gradient centrifugation). Such mobilization may result in the expression of cytochrome b558 on the plasma membrane, as was indicated in this study. Apart from cytochrome b558, several other surface membrane molecules, as we show here for the integrin CD11b/CD18 (CR3), are probably also located in these rapidly mobilizable intracellular vesicles.

Antibodies, Monoclonal↗
PubMed1993

Sequence and functional characterization of a third inositol trisphosphate receptor subtype, IP3R-3, expressed in pancreatic islets, kidney, gastrointestinal tract, and other tissues.

Inositol 1,4,5-trisphosphate (IP3) functions as a second messenger for many neurotransmitters, hormones and growth factors. It causes the release of Ca2+ from intracellular stores by binding to specific receptors that are coupled to Ca2+ channels. Recent studies have shown that there is a family of IP3 receptors, and the complete sequences of two members of this family and partial sequences of two others have been reported. We have determined the complete sequence of a third IP3 receptor, designated IP3R-3, and characterized its pharmacological properties and sites of expression. Rat IP3R-3 is 2670 amino acids in size, has 62 and 64% identity with IP3R-1 and IP3R-2, and is predicted to have a similar structure including a region of eight potential membrane-spanning segments at its COOH terminus, which presumably functions as a Ca2+ channel. Expression of recombinant rat IP3R-3 in COS-7 cells showed that it bound IP3 as well as inositol 1,3,4,5-tetrakisphosphate and inositol hexakisphosphate. Immunohistocytochemical studies of cells expressing recombinant IP3R-3 indicated that it has a preferential cellular distribution in the endoplasmic reticulum. RNA and protein blotting studies indicate that IP3R-3 is expressed in a number of different cultured cell lines including insulin-secreting RINm5F cells. The IP3R-3 is also expressed in adult pancreatic islets, kidney, gastrointestinal tract, and brain. Reverse transcriptase-polymerase chain reaction amplification of IP3R-1, -2, and -3 mRNAs in adult rat pancreatic islets indicated that IP3R-3 was the predominant subtype expressed in this tissue and thus may be responsible for mediating the effects of IP3 on insulin secretion.

Amino Acid Sequence↗
PubMed1993

Biogenesis of von Willebrand factor-containing organelles in heterologous transfected CV-1 cells.

Von Willebrand factor (vWF) is a multimeric protein involved in the adhesion of platelets to an injured vessel wall. vWF is synthesized by the endothelial cell and the megakaryocyte as a precursor protein (pro-vWF) that consists of four repeated domains, denoted D1-D2-D'-D3-A1-A2-A3-D4-B1-B2-B3-C1-C2. Previously, we have defined the domains on the pro-vWF molecule involved in dimerization as well as the domains involved in multimer assembly of vWF dimers. In the endothelial cell, part of the vWF multimers is stored in specialized organelles, the Weibel-Palade bodies. By using immunoelectron microscopy, we demonstrate that upon expression of full-length vWF cDNA, vWF-containing organelles are encountered in monkey kidney CV-1 cells that are morphologically similar to the endothelial-specific Weibel-Palade bodies. Expression in CV-1 cells of a series of vWF cDNA deletion mutants, lacking one or more domains, revealed that only those vWF mutant proteins that are able to assemble into multimers are encountered in dense-cored vesicles. Our data show that this process is independent of a particular domain on vWF and indicate that a 'condensed', multimeric vWF is required for targeting to the Weibel-Palade body.

Amino Acid Sequence↗
PubMed1993

Biochemical characterization and tissue distribution of the A and B variants of the integrin alpha 6 subunit.

Two cytoplasmic variants of the alpha 6 integrin, alpha 6A and alpha 6B, have been identified previously (Hogervorst, F., I. Kuikman, A. G. van Kessel, and A. Sonnenberg. 1991. Eur. J. Biochem. 199:425-433; Cooper, H. M., R. N. Tamura, and V. Quaranta. 1991. J. Cell Biol. 115:843-850). Using synthetic peptides, containing sequences of their cytoplasmic domains, we have produced mAbs specific for either of the variants. These antibodies reacted with a variety of different epithelial tissues. In some tissues (e.g., salivary gland) both variants could be detected while in others only one of the variants was found (e.g., alpha 6A in epidermis and alpha 6B in kidney). Among nonepithelial cells and tissues, perineural fibroblasts and Schwann cells in peripheral nerves and platelets reacted with anti-alpha 6A, while microvascular endothelia reacted with both anti-alpha 6A and anti-alpha 6B. From our immunohistochemical results there is not evidence that combination with beta 1 or beta 4 is restricted to one of the two variants of alpha 6. This was confirmed by immunoprecipitation studies which showed that both beta 1 and beta 4 were coprecipitated by both anti-alpha 6A or anti-alpha 6B antibodies from cells. Also, the distribution of alpha 6A and alpha 6B subunits associated with beta 1 on cells attached to laminin was similar: both were found in focal contacts colocalizing with vinculin. In contrast, the alpha 6A subunit, associated with beta 4 in cultures of a squamous cell carcinoma cell line, was found to codistribute with bullous pemphigoid antigen 230 in hemidesmosomal-like structures. The alpha 6A and alpha 6B variants, immunoprecipitated from various cell lines, exhibited slightly different electrophoretic mobilities. Analysis of the antigens under reducing conditions showed that the mobility of the light chains, but not of the heavy chains, is different. In addition, in some cells the light chains of alpha 6A and alpha 6B, each are of two different sizes. Treatment with N-glycanase showed that these two light chain variants of alpha 6A and alpha 6B are not due to differences in N-linked glycosylation, and may therefore represent alternative proteolytic products of the alpha 6 precursor. We further demonstrate that alpha 6A, but not alpha 6B, is a major target for PMA-induced phosphorylation. Phosphorylated alpha 6A contained phosphoserine and a small amount of phosphotyrosine. There are also two variants of the integrin alpha 3 subunit with different cytoplasmic domains, but in the cell lines examined only alpha 3A could be demonstrated by RT-PCR.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1993

Formation of hemidesmosomes in cells of a transformed murine mammary tumor cell line and mechanisms involved in adherence of these cells to laminin and kalinin.

Keratinocytes attach to an underlying basement membrane by adhesion junctions called hemidesmosomes. We have characterized a cell line, RAC-11P/SD, established from a murine mammary tumor, which differentiates into squamous epithelium and forms well defined hemidesmosomes. These hemidesmosomes contain the integrin alpha 6 beta 4 as well as the hemidesmosomal plaque proteins BP230 and HD1 and are associated with a matrix containing kalinin and laminin. We examined how these cells adhere to laminin and to kalinin present in matrices as well as immunopurified kalinin. We show that adhesion to laminin is energy dependent but does not require an intact actin-containing cytoskeleton. The affinity for kalinin proved to be greater and binding to kalinin was still observed when cells had been treated with deoxyglucose and azide to inhibit metabolic energy. Binding to laminin (or fragment E8), but not to kalinin was partially blocked by a monoclonal antibody specific for the integrin alpha 6 subunit, and only in the initial phase of adhesion. The antibody efficiently blocked adhesion to laminin of cells treated with the microfilament disrupting drug cytochalasin B, but only partially blocked the adhesion of cytochalasin B-treated cells to kalinin, while adherence of cells treated with deoxyglucose and azide to kalinin was blocked completely. The integrin alpha 6 beta 4 is redistributed to the basal surface during adhesion and then is organized into ring-like structures when cells are bound to laminin and localized into hemidesmosomes in cells adhered to kalinin. We suggest that anti-alpha 6 hinders the binding of the alpha 6 beta 4 integrins to its ligands laminin and kalinin, but cannot prevent adhesion when clustering of the integrin has become complete. In addition, there is evidence that adhesion to kalinin is mediated by a second receptor, which associates with the actin-containing cytoskeleton. The presence of such a second receptor is suggested because the cells can spread on kalinin, but not when they have been treated with cytochalasin B. On laminin spreading does not occur, irrespective of whether cells have been treated with cytochalasin B or not. The integrin alpha 3 beta 1, which has been identified as a receptor for kalinin but not for laminin, is strongly expressed in RAC-11P/SD cells and it seems likely that this integrin is responsible for spreading of cells on kalinin.

Animals↗
PubMed1993

Hemodynamic alterations in venous blood flow produced by external pneumatic compression.

Venous stasis associated with prolonged bed rest can enhance the risk of deep venous thrombosis (DVT). Pneumatic compression of the lower extremities can reduce this risk by preventing venous stasis. When selecting a method of leg compression for their patients, physicians must chose between two distinctly different types of compression devices. One device applies pressure with a single-chambered sleeve to the below knee region while the other applies pressure in a sequential gradient fashion from the ankle to the thigh. The current prospective study was designed to evaluated the ability of two such devices to increase blood flow in the profunda femoral vein. Venous blood flow velocity, compression time, and vein diameter were measured in nine normal experimental subjects using an Accuson duplex-Doppler before, during and after leg compression. Compression with the single-chambered device produced a significant rise in venous blood flow velocity; however, this could not be maintained and our results indicate a higher average velocity was achieved with the sequential gradient device. The sequential gradient device also moved a greater volume of blood and achieved a higher average blood flow rate. The time between deflation of the sleeve and return of a phasic respiratory signal was greater after compression with the sequential gradient device. These results suggest that sequential gradient compression produces the type of hemodynamic alterations needed to reduce the risk of DVT by achieving a sustained increase in venous blood flow and more completely emptying of the veins in the leg.

Analysis of Variance↗
PubMed1992

Generation of a panel of somatic cell hybrids containing fragments of human chromosome 12P by X-ray irradiation and cell fusion.

We have employed an irradiation and fusion procedure to generate somatic cell hybrids containing various fragments of the short arm of human chromosome 12 using a 12p-only hybrid (M28) as starting material. For the initial identification of hybrids retaining human DNA, nonradioactive in situ hybridization was performed. Seventeen cell lines appeared to contain detectable amounts of human material. Detailed characterization of these hybrids by Southern blot analysis and chromosomal in situ suppression hybridization (chromosome painting), using hybrid DNAs as probes after Alu element-mediated PCR, resulted in a hybrid panel encompassing the entire chromosome 12p arm. This panel will provide a valuable resource for the rapid isolation of region-specific DNA markers. In addition, this panel may be useful for the characterization of chromosome 12 aberrations in, e.g., human germ cell tumors.

Animals↗