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Biomedical subjects

H Schwarz

Publications and source records attributed to H Schwarz.

At least 91 records · Page 5Linked to original sources
PubMed1996

The nerve growth factor/tumor necrosis factor receptor family.

Receptors in the nerve growth factor/tumor necrosis factor receptor family are characterized by the presence of cysteine-rich motifs of approximately 40 amino acids in the extracellular domain. The ligands are type II transmembrane proteins with beta-strands that form a jelly-roll beta-sandwich. The receptors recognize soluble or cell-surface-bound ligands and mediate diverse cellular responses. Activation of intracellular signals is mediated at least in part by the association of proteins with a RING finger motif or a death domain to the cytoplasmic domains of the receptors. In addition to cell-membrane-bound receptors soluble forms have been described for most of the receptors. Activation of intracellular signals not only occurs through ligand binding to the receptors but cross-linking of at least some members of the ligand family can regulate cell functions.

Animals↗
PubMed1996

Fine structural immunocytochemistry of catenins in amphibian and mammalian muscle.

In adherens junctions, alpha- and beta-catenin serve to link cadherins to the cortical cytoskeleton. Immunofluorescence and immuno-electron microscopy have been applied to elucidate the nature and localization of cadherin/catenin-mediated cell-cell adhesion sites in adult muscle tissues. Antibodies against alpha- and beta-catenin have been used as indicators of such sites in amphibian and mammalian muscle. Intercalated discs are prominent cell-cell adhesion sites in heart muscle. They contain large amounts of the two catenins, the distributions of which are disclosed. In addition and in contrast to their counterparts in guinea pig, cardiomyocytes of Xenopus are also interconnected laterally by catenin-containing cell-cell junctions. These are doublet structures that approach the intercellular contacts of two adjacent cells from both sides and occur in register with the Z-discs. We interpret these structures as catenin/cadherin-based costameres. Ultrastructural details of these structures are described. In addition to its presence in cell-cell adhesion sites, we have found beta-catenin, but not alpha-catenin, in the Z-discs of heart and skeletal striated muscles. In smooth muscle, actin filaments insert into the dense bodies, which are therefore regarded as functional equivalents of the Z-discs. Accordingly, beta-catenin is also found in these structures, again in the absence of alpha-catenin. These non-peripheral intracellular localizations in the Z-discs of striated muscles and the dense bodies of smooth muscle indicate a hitherto unknown function of beta-catenin in these specialized cells.

Animals↗
PubMed1996

Ependymins: meningeal-derived extracellular matrix proteins at the blood-brain barrier.

Ependymins represent regeneration-responsive piscine glycoproteins and in many teleost fish they appear as the predominant cerebrospinal fluid constituents. Thus far, no homologous sequences have been characterized unambiguously in mammals. Sialic acid residues of the N-linked carbohydrate moiety of ependymins are responsible for their calcium-binding capacity. Ependymins from some species bear the L2/HNK-1 epitope typical of many cell adhesion molecules. After their synthesis in fibroblast-like cells of the inner endomeningeal layer, soluble ependymins are widely distributed via the cerebrospinal fluid system. Furthermore, ependymins presumably cross the intermediate endomeningeal barrier layer by way of a transcellular transport phenomenon (transcytosis). A bound form of ependymins is associated with collagen fibrils of the extracellular matrix typically found around cerebral blood vessels. Here, they might modulate the endothelial barrier function. Generally, ependymins are thought to represent a new class of possibly antiadhesive extracellular matrix proteins playing a role in specific cell contact phenomena (e.g., during regeneration).

Amino Acid Sequence↗
PubMed1996

The estrogen-dependent c-JunER protein causes a reversible loss of mammary epithelial cell polarity involving a destabilization of adherens junctions.

Members of the epidermal growth factor (EGF) receptor family are known to be specifically involved in mammary carcinogenesis. As a nuclear target of activated receptors, we examined c-Jun in mammary epithelial cells. For this, we used a c-JunER fusion protein which was tightly controlled by estrogen. Activation of the JunER by hormone resulted in the transcriptional regulation of a variety of AP-1 target genes. Hormone-activated JunER induced the loss of epithelial polarity, a disruption of intercellular junctions and normal barrier function and the formation of irregular multilayers. These changes were completely reversible upon hormone withdrawal. Loss of epithelial polarity involved redistribution of both apical and basolateral proteins to the entire plasma membrane. The redistribution of E-cadherin and beta-catenin was accompanied by a destabilization of complexes formed between these two proteins, leading to an enrichment of beta-catenin in the detergent-soluble fraction. Uninduced cells were able to form three-dimensional tubular structures in collagen I gels which were disrupted upon JunER activation, leading to irregular cell aggregates. The JunER-induced disruption of tubular structures was dependent on active signaling by growth factors. Moreover, the effects of JunER could be mimicked in normal cells by the addition of acidic fibroblast growth factor (aFGF). These data suggest that a possible function of c-Jun in epithelial cells is to modulate epithelial polarity and regulate tissue organization, processes which may be equally important for both normal breast development and as initiating steps in carcinogenesis.

Animals↗
PubMed1996

Sperm morphology assessment using strict criteria and male fertility under in-vivo conditions of conception.

The clinical significance of sperm morphology assessment according to very strict criteria was determined using semen samples of randomly chosen males from couples not submitted to assist procreation techniques, with a median duration of infertility of 4 years (range 1-17; n = 89). The relationships of sperm morphological properties to the results of standard sperm analysis, including the differentiation of round cells in semen by monoclonal antibodies and semen cultures, the testing of sperm functional capacity in vitro with the standardized sperm-cervical mucus penetration test (SCMPT) and the subsequent pregnancy rate under in-vivo conditions of conception, were evaluated in a prospective study. The quick staining method (DiffQuick(R) stain) for sperm morphology proved to be practical and suitable for routine use. The percentage of normal forms according to strict criteria ranged from 1 to 36%, with a median of 12%. Morphological findings were not markedly related to the medical history, but significant relationships between standard parameters of sperm analysis, in particular the sperm count, the progressive motility and standard sperm morphology, were found. The percentage of normal forms was not significantly associated with the microbial colonization of semen samples but was negatively related to high leukocyte rates. Semen samples with a higher percentage of normal spermatozoa (shown, for example, for >4,> 7 or >=14% normal) were significantly more frequent in cases of an adequate SCMPT. The subsequent pregnancy rate within an observation period of 12 months was 20.2%. The pregnancy rate under in-vivo conditions was significantly higher when semen samples had a better sperm morphology, with significant differences for thresholds at 4, 7 and 14% of strictly normal forms. Although sperm morphology is only one among a multiplicity of factors determining fertility, the results suggest that the evaluation of sperm morphology using strict criteria provides valuable information during basic infertility investigations.

Adult↗
PubMed1995

A mRNA variant encoding a soluble form of 4-1BB, a member of the murine NGF/TNF receptor family.

The murine 4-1BB gene, encoding a member of the nerve growth factor/tumor necrosis factor (NGF/TNF) receptor family, is thought to be selectively expressed in T cells and is involved in the regulation of lymphocyte proliferation. We detected two forms of the 4-1BB mRNA by RT-PCR which were expressed in an activation-dependent pattern in splenocytes and thymocytes. cDNA sequencing showed that the smaller form was a mRNA splice variant lacking the transmembrane region (4-1BB delta TM), because of the deletion of exon 8. The two forms of mRNA are differentially expressed in murine T cells, macrophages, 3T3 fibroblasts and epitheloid cells. Northern blotting also identifies two forms of mRNA of 1.5 and 2.4 kb, and the cell-type-specific pattern correlated with the PCR results. These results identify a novel form of 4-1BB. This and the previously known membrane-associated form have a broad tissue distribution, suggesting a more diverse role in host defense.

3T3 Cells↗
PubMed1995

ILA, the human 4-1BB homologue, is inducible in lymphoid and other cell lineages.

We recently identified a gene that is induced by lymphocyte activation (ILA). The sequence of the full-length 1.4-kb cDNA characterized ILA as a new member of the nerve growth factor/tumor necrosis factor (NGF/TNF) receptor family and the human homologue of the murine T-cell-specific receptor 4-1BB. The present study demonstrates ILA mRNA isoforms at 4.4, 4.0, and 1.8 kb in poly-A+ RNA from activated, but not from resting human peripheral blood T lymphocytes. A reverse transcriptase-polymerase chain reaction (RT-PCR) assay was used to study tissue distribution and regulation of ILA expression. The gene was induced in T lymphocytes by phytohemagglutinin (PHA), phorbol myristate acetate (PMA), and antibody to CD3, in B lymphocytes by PMA and antibodies to cell surface Ig, and in blood monocytes by interleukin-1 beta (IL-1 beta), lipopolysaccharide (LPS), and PMA. In T lymphocytes, ILA mRNA was detectable 1.5 hours after stimulation, reached maximal levels at 8 hours, and declined to background levels by 48 hours. Induction of ILA mRNA required protein synthesis and was primarily due to increased transcription. Actinomycin D reduced ILA mRNA levels in activated lymphocytes 50% within 30 minutes, demonstrating a relatively short half-life of this mRNA. Analysis of nonlymphoid cells showed that ILA mRNA was not detectable in resting cells. However, in contrast to the lymphoid-specific expression of the murine 4-1BB gene, ILA was detected in nonlymphoid cells, including epithelial and hepatoma cells after stimulation with IL-1 beta. ILA was not detectable in several brain derived cell lines. The ILA cDNA encodes a 30-kD protein as demonstrated by in vitro translation, and this protein is immunoprecipitated by antisera that were raised against ILA peptides or a glutathione-S-transferase fusion protein. Flow cytometry showed expression of ILA protein on a subset of activated T or B lymphocytes. In conclusion, activation-dependent expression of ILA is found not only in T lymphocytes, but also in B lymphocytes, monocytes, and diverse nonlymphoid cell types.

Amino Acid Sequence↗
PubMed1995

Dendritic cell progenitor is transformed by a conditional v-Rel estrogen receptor fusion protein v-RelER.

A conditional v-Rel estrogen receptor fusion protein, v-RelER, causes estrogen-dependent but otherwise unaltered v-rel-specific transformation of chicken bone marrow cells. Here, we demonstrate that such v-relER-transformed cells exhibit B lymphoid determinants in line with earlier studies on v-rel-transformed cells. However, following inactivation of v-RelER oncoprotein activity by administration of an estrogen antagonist, cells differentiate into antigen-presenting dendritic cells as judged by several morphological and functional criteria. Additionally, under yet different culture conditions, v-relER cells differentiate into cells resembling polymorphonuclear neutrophils. Our studies therefore suggest that the conditional v-RelER, and probably also the authentic v-Rel, transform a common progenitor for neutrophils and dendritic cells.

Animals↗
PubMed1995

Increased number of high sensitive platelets in hypercholesterolemia, cardiovascular diseases, and after incubation with cholesterol.

The number of low density platelets was found to be increased in patients with hypercholesterolemia, as compared with the number in controls. The percentage increase of the low density platelet subpopulation was even more pronounced in patients with hypercholesterolemia when compared with that in patients suffering from myocardial infarction or angina. In vitro studies with control platelets incubated with cholesterol rich liposomes showed also an increase in the subpopulation of low density platelets. After incubation of control platelets with cholesterol rich liposomes, a higher membrane anisotropy and a higher cholesterol to phospholipid (C/P) molar ratio of the plasma membrane were found. Furthermore, cholesterol-enriched platelets were more sensitive upon thrombin stimulation. The results suggest that a shift of platelet subpopulations to a higher number of low density platelets could be caused by either the level of plasma cholesterol or an in-vitro incubation with cholesterol rich liposomes.

Analysis of Variance↗
PubMed1995

Phase and electron microscopic observations of osmotically induced wrinkling and the role of endocytotic vesicles in the plasmolysis of the Gram-negative cell wall.

When a Gram-negative bacterium is challenged with a sufficient concentration of a non-penetrating solute such as sucrose, water is sucked out of the cell. Plasmolysis spaces may form if the cell's cytoplasmic membrane (CM) separates from the murein wall (M) and the outer membrane (OM). However, we suggest that first wrinkling of the wall envelope, forced by dehydration of the cytoplasm, occurs. The cryofixation, freeze-substitution electron microscope studies used here are much too slow to study the kinetics of shrinkage, wrinkling and plasmolysis. However, they are consistent with faster phase microscope studies and previous stopflow experiments. For the electron microscopy studies reported here, only sucrose was used as the osmotic agent and under conditions that do not cause extreme plasmolysis. Plasmolysis spaces were associated with the formation of small membrane-bound vesicles in the nearby cytoplasm. Such vesicles formed by osmotic challenge are called 'endocytotic' in plant cell systems. They had been recorded in earlier plasmolysis studies in bacteria, but not interpreted as a concomitant part of plasmolysis space formation in certain locations of the cell. We suggest that the endocytotic vesicles form because the phospholipid membranes are capable of very little contraction so extra membrane must be disposed of when plasmolysis spaces form. In the case of plasmolysis spaces forming at poles and constriction sites, for geometric reasons the surface area of the CM may be conserved without disposition of excess membrane. We suggest that it is this biophysical property of lipid membranes that leads to the frequent formation of plasmolysis spaces at a pole and at the site of future division. We also observed a novel structure, this is seen only under mild osmotic up-shock, and consists of very thin, straight, uniform and long plasmolysis spaces which were called 'lamellar spaces'; these commonly formed inside the sidewalls and were usually associated with the formation of endocytotic vesicles. Since lipoprotein links the M to the OM layers and thus could affect plasmolysis, we examined both wild-type and deficient strains. Some effects were observed, but they were minimal. The volume of the periplasmic space of growing unshocked cells was determined to be about 7%.

Cell Wall↗
PubMed1995

Identification of receptor binding sites by competitive peptide mapping: phages T1, T5, and phi 80 and colicin M bind to the gating loop of FhuA.

Previously we proposed a transmembrane model of the FhuA receptor protein in the outer membrane of Escherichia coli. Removal of the largest loop at the cell surface converted the FhuA transport protein into an open channel and rendered cells resistant to the FhuA-specific phages T1, T5, and phi 80 and to colicin M. In the present study we employed acetylated hexapeptide amides covering the entire surface loop to investigate binding of the phages and of colicin M. Competitive peptide mapping proved to be a powerful technique to uncover three ligand binding sites within a region of 34 amino acid residues. Hexapeptides derived from three specific regions of the surface loop inhibited infection of cells by the phages and killing by colicin M. Two of these regions were common among all four FhuA ligands. Electron microscopy of phage T5 revealed that one inhibitory peptide triggered a strong conformational change leading to the release of DNA from the phage head. These results suggest that the FhuA gating loop is the target for specific binding of phages T1, T5, and phi 80 and colicin M.

Amino Acid Sequence↗
PubMed1995

Chondrocyte apoptosis induced by nitric oxide.

Chondrocytes stimulated with IL-1 produce high levels of nitric oxide (NO), which inhibits proliferation induced by transforming growth factor-beta or serum. This study analyzes the role of NO and IL-1 in the induction of chondrocyte cell death. NO generated from sodium nitroprusside induced apoptosis in cultured chondrocytes as demonstrated by electron microscopy, 4',6-dianidino-2-phenylindole dihydrochloride staining, FACS analysis, and histochemical detection of DNA fragmentation. Similar results were obtained with two other NO donors, 3-morpholinosynonimide-hydrochloride and s-nitroso-N-acetyl-D-L-penicillamine. In contrast, oxygen radicals generated by hypoxanthine/xanthine oxidase caused necrosis but did not induce chondrocyte apoptosis. To analyze whether endogenously generated NO induces apoptosis, chondrocytes were stimulated with IL-1, but there was no evidence for apoptotic changes. Combinations of NO inducers such as IL-1, lipopolysaccharide, tumor necrosis factor, and interferon-gamma also failed to trigger apoptosis. IL-1-stimulated chondrocytes are known to produce oxygen radicals that react with NO to form products that can induce cell death in other systems. We thus tested IL-1 in combination with the oxygen radical scavengers N-acetyl cysteine, dimethyl sulfoxide, or 5,5'-dimetylpyrroline 1-oxide. Under these conditions IL-1 was able to induce apoptosis, which was inhibited in a dose-dependent manner by the NO synthase inhibitor N-monomethyl L-arginine. Conversely, endogenous oxygen radicals induced by inflammatory mediators caused necrosis under conditions in which the simultaneous production of NO was reduced. These results suggest that NO, but not oxygen radicals, is the primary inducer of apoptosis in human articular chondrocytes.

Adult↗
PubMed1994

The motility signal of scatter factor/hepatocyte growth factor mediated through the receptor tyrosine kinase met requires intracellular action of Ras.

Scatter factor/hepatocyte growth factor (SF/HGF) has various biological effects upon different cells, i.e. induces increased motility and proliferation as well as invasiveness and morphogenesis. The signals given to epithelial cells by SF/HGF are all mediated through the Met receptor tyrosine kinase (Weidner, K. M., Sachs, M., and Birchmeier, W. (1993) J. Cell Biol. 111, 145-154) suggesting that signal diversity is due to the interplay of different downstream pathways. It has also been shown that SF/HGF activates the protooncogene product Ras, i.e. stimulates guanine nucleotide exchange. In order to examine whether Ras is involved in mediating the dissociation and motility signal of SF/HGF to epithelial cells, we have expressed in Madin-Darby canine kidney cells the dominant-negative N17Ras under the control of a modified metallothionein promoter. Induced expression of N17Ras by the addition of Zn2+ clearly prevented dissociation of the cells by SF/HGF. These data indicate that the Ras pathway is indeed essential to mediate the motility signal of SF/HGF-Met to the cell-cell adhesion system and the cytoskeleton of epithelial cells.

Animals↗
PubMed1994

Neuropeptide Y is an inducible gene in the human immune system.

This study reports on neuropeptide Y (NPY) mRNA expression in human peripheral blood mononuclear cells (PBMC) and lymphoid tissues. By reverse transcription polymerase chain reaction (RT-PCR) it is shown that activated human PBMC of normal blood donors expressed the NPY gene. The PCR products had the expected size and Northern blotting demonstrated the presence of the 0.8-kb NPY mRNA. To define the subpopulations of mononuclear cells expressing this neuropeptide, purified monocytes, B cells and T cells were stimulated with specific activators. Monocytes and in vitro matured macrophages expressed NPY mRNA in response to phorbol myristate acetate (PMA). B lymphocytes expressed NPY mRNA following stimulation with antibody to surface immunoglobulin and PMA. In order to analyze whether these cell types express NPY under physiological conditions in vivo, human bone marrow, tonsil and thymus were analyzed. In situ hybridization of bone marrow revealed a small number of cells containing high levels of NPY mRNA which was also detected in RNA extracts of human thymus and tonsil. In summary, NPY is an inducible gene in human lymphocytes and monocytes and it is expressed at sites where these cells are activated in vivo.

Animals↗
PubMed1994

Anadamide, an endogenous cannabinoid receptor agonist inhibits lymphocyte proliferation and induces apoptosis.

This study examined the immunoregulatory effects of anadamide, the recently identified first endogenous cannabinoid receptor ligand. Anadamide caused dose-dependent inhibition of mitogen-induced T and B lymphocyte proliferation. Its potency was 3- and 10-fold less than that of the synthetic cannabinoids delta 8-tetrahydrocannabinol (delta 8-THC) and CP55940, respectively. Anadamide effects on DNA synthesis in T and B lymphocytes occurred rapidly as exposure of the cells during the final 4 h of culture was sufficient to achieve > 40% inhibition. Low doses of anadamide which caused significant inhibition of lymphocyte proliferation caused DNA fragmentation as demonstrated by immunohistochemistry, FACS analysis and Southern blotting. Apoptosis was also induced by high concentrations of delta 8-THC, but not by CP55940. Brain and peripheral cannabinoid receptor mRNA was expressed in PBMC with varying levels between individual donors. In summary, these findings demonstrate immunosuppressive effects of anadamide which are associated with inhibition of lymphocyte proliferation and the induction of cell death by apoptosis.

Adjuvants, Immunologic↗
PubMed1994

[Localized pleural mesothelioma].

About 500 cases of localized pleural mesothelioma are known from the literature. These benign or malignant tumors arise most frequently from the visceral pleura, rarely from the pericardium. They are not associated with asbestos. Correct diagnosis is rarely made preoperatively. Resection is the treatment of choice and can be curatively even in the malignant type. Clinical, radiological and pathological findings, therapy and prognosis are described.

Aged↗