Biomedical subjects

M Husmann

Publications and source records attributed to M Husmann.

31 records · Page 2Linked to original sources

PubMed1994

Helicobacter sp. strain Mainz isolated from an AIDS patient with septic arthritis: case report and nonradioactive analysis of 16S rRNA sequence.

A campylobacter-like organism was isolated from an effusion of the left knee joint of an AIDS patient 2 weeks after bacteremia with a morphologically identical organism. Amplified genomic 16S rRNA sequences were analyzed by a nonradioactive blotting technique. The closest match was found with Helicobacter fenelliae (97.7% homology). Sequence data and phenotype suggest that the isolate may represent a so far unrecognized species of the genus Helicobacter.

Acquired Immunodeficiency Syndrome↗

PubMed1992

A retinoic acid response element from the rat CRBPI promoter is activated by an RAR/RXR heterodimer.

The expression of the rat cellular retinol binding protein I (rCRBPI) can be upregulated in vivo by retinoic acid (RA). Here we have analyzed the rCRBPI promoter region and compared it to the corresponding mouse sequence. We find that the CRBPI 5' flanking region has been highly conserved between rat and mouse, including a RA response element (RARE) approximately 1 kb upstream of the start of transcription. The RARE is of the direct repeat type with a two nucleotide spacer. Like other direct repeat RAREs, this response element is activated by RAR alpha and beta but not by RAR gamma 1. Furthermore, the rCRBPI-RARE is most effectively activated when both RAR and RXR are present. In addition RAR/RXR heterodimers are required for efficient binding to the rCRBPI-RARE, while RARs or RXR alone do not interact effectively with this response element. The rCRBPI gene is therefore most likely activated in vitro by a RAR/RXR heterodimer.

Animals↗

PubMed1991

Identification of retinoids with nuclear receptor subtype-selective activities.

Retinoic acid (RA) and its synthetic analogues, retinoids, have shown promising results in the prevention of epithelial carcinogenesis and in the treatment of acute promyelocytic leukemia and various proliferative skin disorders. Retinoid action on gene regulation is mediated by three distinct nuclear retinoic acid receptor subtypes, RA receptors alpha, beta, and gamma. The existence of multiple RA receptors has raised the possibility that receptor subtype-specific retinoids with reduced side effects can be developed. To analyze the activity of retinoids at the molecular level, we used a receptor activation assay. RA and 22 retinoids were compared on the three receptor subtypes. We found the alpha receptor to be least sensitive to activation by RA and the gamma receptor to be most sensitive. Compared with RA, one of the retinoids showed increased activity for the alpha and beta receptors. Three retinoids revealed no gene activation activity and showed no antagonistic effects when assayed in the presence of RA. Surprisingly, several of the retinoids were efficient activators of the beta and gamma receptors but poor activators or nonactivators of the alpha receptor. Our data demonstrate that the three RA receptor subtypes have differential ligand activation specificities and that the design of receptor subtype-selective retinoids is possible.

Animals↗

PubMed1991

Novel pathway for thyroid hormone receptor action through interaction with jun and fos oncogene activities.

Many essential biological pathways, including cell growth, development, and metabolism, are regulated by thyroid hormones (THs). TH action is mediated by intracellular receptors that belong to a large family of ligand-dependent transcription factors, including the steroid hormone and retinoic acid receptors. So far it has been assumed that TH receptors (TRs) regulate gene transcription only through the classical protein-DNA interaction mechanism. Here we provide evidence for a regulatory pathway that allows cross-talk between TRs and the signal transduction pathway used by many growth factors, oncogenes, and tumor promoters. In transient transfection studies, we observed that the oncogenes c-jun and c-fos inhibit TR activities, while TRs inhibit induction of the c-fos promoter and repress AP-1 site-dependent gene activation. A truncated TR that lacks only 17 amino acids from the carboxy terminus can no longer antagonize AP-1 activity. The cross-regulation between TRs and the signal transduction pathway appears to be based on the ability of TRs to inhibit DNA binding of the transcription factor AP-1 in the presence of THs. The constituents of AP-1, c-Jun, and c-Fos, vice versa, can inhibit TR-induced gene activation in vivo, and c-Jun inhibits TR DNA binding in vitro. This novel regulatory pathway is likely to play a major role in growth control and differentiation by THs.

Base Sequence↗

PubMed1991

Antagonism between retinoic acid receptors.

In the developing mouse, retinoic acid receptors (RARs) beta and gamma 1 are expressed in characteristic spatiotemporal patterns which are correlated with different developmental fates of the respective tissues. Understanding the cues that regulate the expression of the various RARs may therefore provide insights into the process of tissue diversification. Transcription of RAR beta is rapidly upregulated through a retinoic acid-responsive element (here referred to as the beta RARE) in its promoter. Like RAR alpha and RAR beta, RAR gamma 1 has been implicated in the activation of the beta RARE. Therefore, it is puzzling that RAR beta and RAR gamma 1 appear to be expressed in reciprocal patterns. In the present report, we show that RAR gamma 1, one of the two predominant RAR gamma isoforms, can inhibit the activity of RAR gamma 2, RAR beta, and endogenous RAR on the beta RARE. In contrast, the three RAR gamma isoforms tested and RAR beta activated a palindromic thyroid hormone response element with similar levels of efficiency. The differential activity of RAR gamma 1 compared with that of RAR beta appears to reside in both the N-terminal and the C-terminal halves of RAR gamma 1. RAR gamma 1-mediated inhibition of other RARs may involve competition for the response element as well as direct interaction with other receptors and might be part of a regulatory system contributing to the characteristic tissue distribution of the various RARs.

Animals↗

PubMed1990

Embryonic neural cell adhesion molecule in cerebrospinal fluid of younger children: age-dependent decrease during the first year.

Poly-alpha-2,8-N-acetylneuraminic acid (poly-alpha-2,8-NeuAc) is developmentally expressed in neural tissue of higher animals, where it is covalently attached to the neural cell adhesion molecule (NCAM), a large integral membrane glycoprotein mediating cell-cell adhesion during neuronal development. NCAM exists in several molecular forms, of which only embryonic NCAM carries lengthy chains (n greater than 5) of poly-alpha-2,8-NeuAc. Chemically identical poly-alpha-2,8-NeuAc of bacterial origin is an important virulence factor in infections caused by Neisseria meningitidis group B and Escherichia coli K1, the predominant pathogens of bacterial meningitis. A quantitative enzyme-linked immunoassay was developed using monoclonal antibody (MAb) 735, an MAb specifically recognizing poly-alpha-2,8-NeuAc, and applied to CSF specimens from younger children. Poly-alpha-2,8-NeuAc contents were within the range of 20-0.2 micrograms/ml, decreasing from day 1 to day 300. Immunoprecipitation, immunoblot with a rabbit anti-mouse NCAM serum recognizing the protein part of human NCAM by cross-reactivity, affinity enrichment using immobilized MAb 735, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that poly-alpha-2,8-NeuAc in CSF is bound to human NCAM, probably NCAM-120.

Antigens, Surface↗

PubMed1990

Immunohistochemical localization of polysialic acid in tissue sections: differential binding to polynucleotides and DNA of a murine IgG and a human IgM monoclonal antibody.

For immunolocalization of alpha(2-8)-linked polysialic acid, which forms part of the neural cell adhesion molecule (N-CAM), two monoclonal antibodies, MAb735 and IgMNOV, were employed. Both antibodies have previously been shown to bind the extremely low immunogenic capsular polysaccharide of group B meningococci, which also consists of alpha(2-8) polysialic acid, but not to other, even closely related forms of polysialic acid. Despite the identical polysaccharide specificity of these two MAb, we observed marked differences of the staining pattern in tissue sections. We showed that these differences in immunostaining were due to the crossreactivity of IgMNOV with polynucleotides and DNA. MAb735, however, was shown to react exclusively with alpha(2-8) polysialic acid. Moreover, the specificity of MAb735 proved to be unique among eleven other MAb directed against various bacterial polysaccharides, as it was the only one unreactive with polynucleotides. Thus, MAb735, the only IgG type mouse monoclonal antibody to polysialic acid thus far reported, can be considered a specific probe for the unambiguous detection of alpha(2-8) polysialic acid in tissue sections, and should therefore help to further elucidate the role of polysialic acid in developmental processes.

Animals↗

PubMed1990

A retinoic acid receptor-specific element controls the retinoic acid receptor-beta promoter.

The morphogen retinoic acid (RA) regulates gene transcription by interacting with specific nuclear receptors that recognize DNA sequences near responsive promoters. While much has recently been learned about the nuclear receptor proteins, little is known about the genes that are directly regulated by RA and their cis-acting response elements recognized by these receptors. Here we have analyzed the RA receptor-beta (RAR beta) gene promoter that is controlled by RA. We find that a RA-responsive element (RARE) is located adjacent to the TATA box. The RARE shows a direct repeat symmetry which is essential for its function. While thyroid hormone-responsive elements can also function as RAR response elements, we show here that this RARE is activated by endogenous RARs and RAR beta, but cannot be regulated by thyroid hormone receptors and other known nuclear receptors. In addition, we find that RAR gamma is a poor activator of this RARE. However, the response element is bound with high affinity by both RAR beta and RAR gamma as well as by thyroid hormone receptors. Thus, interaction between specific response elements and receptors is insufficient for gene activation.

Base Sequence↗

PubMed1989

Embryonic neural cell adhesion molecules on human natural killer cells.

The neural cell adhesion molecules (NCAM) are surface glycoproteins that were first described in brain tissue. NCAM mediate adhesion in a variety of cell-cell interactions. In the present study we show that the so-called "embryonic" NCAM, i.e., the highly polysialylated forms of these proteins, are expressed on natural killer cells and some CD3+ cells in man. Homotypic binding of NCAM, believed to be of importance for cell-cell adhesion in neural tissues, appears not to be essential for NK cell-mediated killing. Yet, NCAM might be involved in NK cell migration, homing or related functions.

Antibodies, Monoclonal↗

PubMed1989

Up-regulation of embryonic NCAM in an EC cell line by retinoic acid.

The impact of retinoic acid (RA) on the expression of the neural cell adhesion molecules (NCAMs) and their developmentally regulated polysialic acid (PSA) moiety was studied in embryonal carcinoma (EC) cell lines. These cell lines are known to be capable of RA-induced differentiation into neurons (murine P19 cells) or parietal endoderm (murine F9 cells), respectively. Monoclonal antibodies were employed to monitor expression of NCAM and PSA. F9 and P19 cells were both found to express NCAM but only P19 cells carried the highly polysialylated "embryonic form" of NCAM (E-NCAM). The amount of NCAM in aggregated P19 cells but not in F9 cells was dramatically increased upon treatment with RA. Since NCAMs play an important role in cell interactions during embryogenesis it is tempting to speculate that the regulative impact of RA on NCAMs is related to its morphogenic property.

Cell Adhesion Molecules, Neuronal↗

PubMed1988

Expression of cell adhesion molecules in the olfactory system of the adult mouse: presence of the embryonic form of N-CAM.

The expression of the neural cell adhesion molecules N-CAM and L1 was investigated in the olfactory system of the mouse using immunocytochemical and immunochemical techniques. In the olfactory epithelium, globose basal cells and olfactory neurons were stained by the polyclonal N-CAM antibody reacting with all three components of N-CAM (N-CAM total) in their adult and embryonic states. Dark basal cells and supporting cells were not found positive for N-CAM total. The embryonic form of N-CAM (E-N-CAM) was only observed on the majority of globose basal cells, the precursor cells of olfactory neurons, and some neuronal elements, probably immature neurons, since they were localized adjacent to the basal cell layer. Differentiated neurons in the olfactory epithelium did not express E-N-CAM. In contrast to N-CAM total, the 180-kDa component of N-CAM (N-CAM180) and E-N-CAM, L1 was not detectable on cell bodies in the olfactory epithelium. L1 and N-CAM180 were strongly expressed on axons leaving the olfactory epithelium. Olfactory axons were also labeled by antibodies to N-CAM180 and L1 in the lamina propria and the nerve fiber and glomerular layers of the olfactory bulb, but only some axons showed a positive immunoreaction for E-N-CAM. Ensheathing cells in the olfactory nerve were observed to bear some labeling for N-CAM total, L1, and N-CAM180, but not E-N-CAM. In the olfactory bulb, L1 was not present on glial cells. In contrast, N-CAM180 was detectable on some glia and N-CAM total on virtually all glia. Glia in the nerve fiber layer were labeled by E-N-CAM antibody only at the external glial limiting membrane. In the glomerular layer, E-N-CAM expression was particularly pronounced at contacts between olfactory axons and target cells. The presence of E-N-CAM in the adult olfactory epithelium and bulb was confirmed by Western blot analysis. The continued presence of E-N-CAM in adulthood on neuronal precursor cells, a subpopulation of olfactory axons, glial cells at the glia limitans, and contacts between olfactory axons and their target cells indicates the retention of embryonic features in the mammalian olfactory system, which may underlie its remarkable regenerative capacity.

Animals↗

PubMed1983

Identification and characterization of gp TFA-1, a guinea pig T cell surface antigen associated with T cell function.

Monoclonal antibodies (Ab) were produced that specifically recognized guinea pig T cells. FACS analysis revealed that Ab 188 bound to the majority of peripheral T lymphocytes of strain 2 and strain 13 guinea pigs and to a minor population of thymocytes. It failed to react with the Ia-bearing guinea pig B cell leukemia line EN-L2C, with macrophages, bone marrow cells, erythrocytes, or thrombocytes. Treatment of T cells with Ab 188 and complement prevented T cell activation. Culturing primed T cells with antigen- or mitogen-pulsed syngeneic or with allogeneic macrophages in the continuous presence of Ab 188 produced a marked, dose-dependent inhibition of T cell proliferation. The antigen defined by Ab 188 was therefore designated guinea pig T lymphocyte function-associated antigen-1, gp TFA-1. The magnitude of inhibition by Ab 188 varied between 65 and 85% whereas three other antibodies to guinea pig T cells had no inhibitory effect on T cell proliferation. Time course experiments revealed that gp TFA-1 is critically involved in an early phase of T cell activation. Maximal inhibition was achieved only if the antibody was present from the beginning of the cell culture; the addition of antibody after 24 hr of culture no longer had an inhibitory effect. Ab 188 did not induce T cell mitogenesis. Two-dimensional analysis (one-dimensional, IEF; two-dimensional, SDS-PAGE) of immunoprecipitates obtained from NP40 lysates of [35S]methionine-labeled T cell blasts indicated that a molecule was specifically precipitated that consisted of two noncovalently associated polypeptide chains with apparent m.w. of 43,000 and 38,000. Both subunits displayed extensive charge heterogeneity focusing at an average isoelectric point of 5.0 and 6.5, respectively. The gp TFA-1 molecule exhibits striking similarities in its functional and structural properties to recently described clonotypically expressed T cell glycoproteins, which were shown to be involved in antigen recognition by T cells in the murine and human systems.

Animals↗

PubMedDate not supplied

Infection of the upper extremity by Mycobacterium marinum in a 3-year-old boy--diagnosis by 16S-rDNA analysis.

A 3-year-old boy developed several subcutaneous nodular lesions on his right arm. Based on the histological examination of one of these nodules furunculosis was suspected and cefuroxime was tentatively given. However, acid-fast bacilli were then detected in the tissue specimen and a few colonies of acid fast, gram-positive rods grew on blood agar. Definitive species diagnosis (Mycobacterium marinum) was rapidly achieved by automated sequencing of amplified 16S-rDNA and antimicrobial therapy was adjusted according to the available literature. After 3 weeks of treatment with clarithromycin, rifampicin and protionamid regression of the nodular lesions was evident.

Arm↗