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Biomedical subjects

M Bachmann

Publications and source records attributed to M Bachmann.

At least 109 records · Page 6Linked to original sources
PubMed1991

Susceptibility of primary human glial fibrillary acidic protein-positive brain cells to human immunodeficiency virus infection in vitro: anti-HIV activity of memantine.

Primary human glial fibrillary acidic protein-positive (GFAP+) brain cells (enriched population) have successfully been infected with human immunodeficiency virus type 1 (HIV-1) in vitro, when cocultivated with HIV-1-producing H9 cells. Direct incubation of brain cells with HIV-1 resulted only in a limited infection. The percentage of HIV+ cells increased from 5% in passage 1 to 40% in passage 8. Simultaneously with the increase of infected cells, the reverse transcriptase activity in the culture medium increased and reached maximal values in passage 8. The infected cells also produced intact viral particles. In the early phase of cultivation the HIV-infected cells displayed a significantly higher proliferation rate than the uninfected controls. At passage number 8 the HIV-infected GFAP+ cells had almost totally lost the ability to grow, while the controls proliferated at a rate almost unimpaired from the beginning of the cultivation. Up to 10 to 15% of the HIV-infected GFAP+ cells contained at passage number 5 more than 3 nuclei. Memantine (1-amino-3,5-dimethyladamantane), a blocker of the N-methyl-D-aspartate receptor channels, was found to display a significant anti-HIV effect (at a concentration of 1 microgram/ml) on enriched cultures of GFAP+ cells in vitro.

Antiviral Agents↗
PubMed1991

Grain dust and respiratory health in South African milling workers.

Respiratory health was investigated in 224 grain milling workers. The likelihood of respiratory symptoms and chronic airflow limitation was raised for workers exposed to dust independent of the effects of smoking. Smokers were more likely than non-smokers to respond to a bronchodilator at the end of the working week. Dust was more strongly associated with most abnormal outcomes than was smoking. Subjective categories of exposure to dust were more strongly associated with most abnormal outcomes than were objective categories. The prevalence of all symptoms at the time of a survey conducted at the mill six years before was higher in workers who subsequently left the mill than in those who remained employed although the differences were not significant.

Adult↗
PubMed1991

Translocation of the nuclear autoantigen La to cell surface: assembly and disassembly with the extracellular matrix.

La (SS-B) protein is known as one major antigenic target for autoantibodies from patients with certain autoimmune diseases such as Sjogren's syndrome or Lupus Erythematosus. La protein belongs to the so called "extractable nuclear antigens". Here we report that La antigen is not restricted to the nucleus as one might deduce from the exclusive nuclear staining pattern of patient anti-La antibodies but after stimulation of serum-starved cells with 10% fetal calf serum (FCS) appears and stays for at least 45 min at the outer surface of CV-1 cells being available for binding of anti-La antibodies. In addition we found that a minor part of La antigen associates with the extracellular fibronectin network. After addition of 10% FCS to serum starved cells this extracellular autoantigen disassembled from the extracellular matrix and was taken up again by the cells. Incubation of serum starved cells with mercuric chloride, a known potent inducer of autoantibodies, also resulted in a detachment of the extracellular matrix associated La protein. From our studies it becomes likely that La protein itself is the antigen during autoimmunization. Moreover, once developed, anti-La antibodies might be able to bind to cell surface expressed La protein resulting in a damage of these cells leading to the inflammational events known to occur during disease.

Autoantigens↗
PubMed1991

Antibodies against defined carbohydrate structures of Candida albicans protect H9 cells against infection with human immunodeficiency virus-1 in vitro.

In this study we raised antibodies against Candida albicans mannans of serotype A and B which comprise mannose alpha(1----2)-and mannose alpha(1----3)-linked residues. These antibodies inhibited human immunodeficiency virus type IIIB (HIV-IIIB) infection of H9 cells in vitro; 5 micrograms/ml of antibodies against mannan from serotype A and 10 micrograms/ml of antibodies against serotype B mannan were sufficient to inhibit infection by almost 100 and 85%, respectively, after an incubation period of 4 days. During a prolonged incubation period (8-12 days), the amount of HIV particles (as measured by reverse transcriptase activity in the culture medium) increased again in assays with antibodies raised against serotype B, but only little in assays containing antibodies against serotype A. Applying the Western blotting technique and a novel enzyme-linked immunosorbent assay system it was established that the antibodies reacted with the gp120 of HIV-1 exclusively. Immunofluorescence inspection using a confocal laser scanning microscope revealed that the gp120 protein is exposed on the outer surface of H9 cells where it is recognized by the anti-mannan antibodies. These results indicate that mannan residues of C. albicans can serve as antigens to raise neutralizing antibodies against HIV infection.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Endogenous retroviral elements in human DNA.

Endogenous retroviruses and retroviral elements represent a substantial component of vertebrate genomes. They are inherited as stable Mendelian genes and may be activated spontaneously or by physical or chemical agents. In the human genome various retroviral elements have been detected by their relationship with mammalian endogenous and exogenous retroviruses. The structure of these elements resembles either full-length or truncated proviruses. The biological function of human retrovirus-related sequences is still unknown, but like other transposable elements, they may have contributed in shaping the eukaryotic genome. Furthermore, they exhibit a number of features giving them a potential for involvement in carcinogenesis. Expression of endogenous retroviral elements has been detected in various human tissues and cell lines and in some cases appears to be associated with human neoplasias.

DNA, Viral↗
PubMed1990

Correlation of anti-cytoskeleton antibody activities in synovial fluid with interleukin-6 in patients with osteoarthritis and inflammatory joint disease.

Synovial fluids and sera from patients with rheumatoid arthritis, psoriatic arthritis, yersinia arthritis, Behçet's syndrome, Crohn's disease, and osteoarthritis were tested for antinuclear antibodies and antibodies to five cytoskeletal components in sensitive enzyme-linked immunosorbent assay (ELISA) systems and for IL-6 concentrations in a proliferation assay (IL-6 dependent hybridoma cell line B13.29, subclone B9). Statistically significant correlations between antibody activities and IL-6 levels were found for vimentin antibodies (r = 0.56; p less than 0.05) and actin antibodies (r = 0.44; p less than 0.05). In patients with chronic and active disease like rheumatoid arthritis and psoriatic arthritis, optical densities measured by vimentin- and actin-ELISA were significantly different from those measured in patients with osteoarthritis. To date only a few reports exist concerning the incidence of antibodies in synovial fluids. We have shown to our knowledge for the first time that IL-6 seems to induce synovial fluid antibody activities restricted to cytoskeletal components of synoviocytes (i.e., vimentin and actin). Synovial fluid antibody activities against vimentin and actin appear to be markers of activity in patients with inflammatory joint disease.

Actins↗
PubMed1990

Differential effect of insulin and epidermal growth factor on the mRNA translocation system and transport of specific poly(A+) mRNA and poly(A-) mRNA in isolated nuclei.

The efficiency of efflux of rapidly labeled poly(A)-containing mRNA from isolated rat liver nuclei was found to be modulated by insulin and epidermal growth factor (EGF) in a biphasic but opposite way. At physiological concentrations (10 pM insulin and 1 pM EGF), maximal stimulation of the transport rate by insulin (to 137%) and maximal inhibition by EGF (to 69%) were obtained; at higher concentrations (greater than 100 pM and greater than 10 pM, respectively), the amount of poly(A)-containing mRNA released into the postnuclear supernatant was nearly identical with the level found in untreated nuclei (= 100%). Using mRNA entrapped into closed nuclear envelope (NE) vesicles as a model system, it was found that the modulation of nuclear efflux of mRNA by the two growth factors occurs at the level of translocation through the nuclear pore. The NE nucleoside-triphosphatase (NTPase) activity, which is thought to mediate nucleocytoplasmic transport of at least some mRNAs, responded to insulin and EGF in the same manner as the mRNA transport rate. The increase in NTPase activity caused by insulin and the decrease in NTPase activity caused by EGF were found to be due to changes of the maximal catalytic rate; the Michaelis constant of the enzyme remained almost constant. Investigating the effect of the two growth factors on transport of specific mRNAs, poly(A)-containing actin mRNA was found to display the same alteration in efflux rate as rapidly labeled, total poly(A)-containing mRNA. In contrast, efflux of histone H4 mRNA, which lacks a 3'-poly(A) sequence, decreased in response to insulin and reached minimum levels at the same concentration at which maximum levels of actin mRNA transport rate were obtained. Studying the mechanism of action of insulin and EGF on NE mRNA translocation system, insulin was found to cause an enhancement of NE-associated phosphoprotein phosphatase activity, resulting in a dephosphorylation of the NE poly(A) binding site (= mRNA carrier) and, hence, in a decrease in its affinity to poly(A) [the poly(A) binding affinity of the poly(A)-recognizing mRNA carrier within the envelope is increased after phosphorylation]. EGF, on the other hand, stimulated the protein kinase, which phosphorylates the carrier, and, hence increased the NE poly(A) binding affinity. Because the stage of phosphorylation of the mRNA carrier (which is coupled with the NTPase within the intact NE structure) is inversely correlated with the activity of the NTPase, an enhancement of poly(A)-containing mRNA transport rate by insulin and an inhibition by EGF are observed.

Adenosine Triphosphate↗
PubMed1990

Characterization of the autoantigen La as a nucleic acid-dependent ATPase/dATPase with melting properties.

The autoantigen La, a known transcription termination factor of RNA polymerase III, was purified to homogeneity from mouse 3T3 cells and calf thymus by different isolation procedures. The La protein from calf thymus was separated into RNA binding and nonbinding subclasses. The murine La protein and the RNA binding subclass of calf thymus La protein showed ATPase/dATPase activity in the presence of DNA-RNA or RNA-RNA hybrids. A novel monoclonal anti-La antibody (La11G7) and patients' anti-La antibodies immunoadsorbed to homogeneously purified La protein were able to inhibit the enzyme activity of La protein. La protein was able to melt a synthetic DNA-RNA hybrid in a reaction that required ATP hydrolysis. The RNA binding ability of the nonbinding subclass was restored by treatment with sialidase. This treatment also restored the protein's ATP-dependent melting activity.

Adenosine Triphosphatases↗
PubMed1990

Evidence for involvement of a nuclear envelope-associated RNA helicase activity in nucleocytoplasmic RNA transport.

It seems well established that translocation of at least some mRNAs through the nuclear pore is (1) an energy-dependent process, and (2) dependent on the presence of the poly(A) segment attached to most mRNA species. We describe that RNA helicase (RNA duplex unwindase) activity is present in a nuclear envelope (NE) preparation, which also appears to be involved in nucleocytoplasmic RNA transport. This activity unwinds RNA: RNA hybrids. The helicase has a pH optimum of 7.5 and a temperature optimum of 30 degrees C. Applying the sealed NE vesicle system, it was shown that duplex RNA species are readily released from the vesicles in an unidirectional manner, in contrast to single-stranded RNA, which is much slower transported into the extravesicular space. Attachment of a poly(A) segment to the RNA duplex additionally increases the efflux rate of this RNA. Efflux of duplex RNA but not efflux of single-stranded RNA was strongly inhibited by formycin B 5'-triphosphate. Our results suggest that, besides poly(A), duplex structures, if present in a given RNA, modulate and control the export of RNA.

Animals↗
PubMed1990

Shuttling of the autoantigen La between nucleus and cell surface after uv irradiation of human keratinocytes.

During the past years we have established that the nuclear autoantigen La shuttles between the nucleus and the cytoplasm in tumor cells after inhibition of transcription or virus infection. We reinvestigated this shuttling using primary human keratinocytes from both healthy donors and patients with xeroderma pigmentosum. Ultraviolet irradiation resulted in both an inhibition of transcription and a translocation of La protein from the nucleus to the cytoplasm. After a prolonged inhibition of transcription La protein relocated into the nucleus and assembled with nuclear storage regions. The uv-induced shuttling included a translocation to the cell surface, where La protein colocalized with epidermal growth factor receptors.

Autoantigens↗
PubMed1990

Adhesive fimbriae produced in vivo by Escherichia coli O139:K12(B):H1 associated with enterotoxaemia in pigs.

Two strains of E. coli O139:K12 (B):H1 were compared in vitro and in the intestinal environment. Both strains colonized the small intestines of experimentally inoculated pigs and exhibited in vivo a similar relationship to the microvillus border as enterotoxigenic E. coli (ETEC). Strain 107/86 grown on blood agar expressed numerous long flexible non-haemagglutinating fimbriae which were antigenically distinct from the known fimbriae of porcine ETEC. It adhered in vitro to porcine enterocyte brush border fragments. Strain 124/76 grown on blood agar was devoid of fimbriae and did not adhere to brush border fragments. However, fimbriae morphologically and antigenically indistinguishable from those of strain 107/86 were detected in the intestinal environment by direct immunofluorescence and by immuno electron microscopy.

Animals↗
PubMed1990

Predictive value of FRC and respiratory compliance on pulmonary gas exchange induced by high frequency jet ventilation in humans.

To determine if functional residual capacity (FRC), compliance of the respiratory system (C), or underlying pulmonary disease are predictive for the efficacy of high frequency jet ventilation (HFJV) on pulmonary gas exchange, we investigated six adult patients within 4 h of abdominal surgery and six patients with severe adult respiratory distress syndrome. Gas exchange during intermittent positive pressure ventilation (IPPV) was compared with that during HFJV at frequencies of 100 b.p.m. (HFJV100) and 200 b.p.m. (HFJV200), resulting in a minute ventilation of about 400 ml kg-1 with both ventilatory frequencies, and in both groups of patients. Baseline FRC and C were measured during IPPV with the multiple-breath nitrogen washout method and from expiratory pressure-volume curves, respectively. Changes in the alveolar-arterial oxygen difference (PAO2 - PaO2): FIO2 ratio induced by HFJV correlated negatively with C (HFJV100: r = -0.78, P less than 0.005; HFJV200: r = -0.84, P less than 0.005); that is, greater oxygenation was obtained in patients with a better compliance. Similarly, changes in arterial partial pressure of carbon dioxide (PaCO2) induced by HFJV correlated negatively with C (HFJV100: r = -0.77, P less than 0.001; HFJV200: r = -0.61, P less than 0.05). In contrast, there was no significant correlation between FRC measured during IPPV and changes in (PAO2 - PaO2): FIO2 ratio or PaCO2 induced by HFJV, as these changes were influenced more by the patient's pulmonary disease than by baseline FRC. These results should be interpreted in the context of different underlying pathophysiological mechanisms reducing FRC in both groups of patients.

Abdomen↗
PubMed1989

Energy requirement and kinetics of transport of poly(A)-free histone mRNA compared to poly(A)-rich mRNA from isolated L-cell nuclei.

ATP-promoted efflux of poly(A)-rich RNA from isolated nuclei of prelabeled mouse lymphoma L5178y cells has an activation energy of 51.5 kJ/mol, similar to that found for the nuclear envelope nucleoside triphosphatase (48.1 kJ/mol) assumed to be involved in mediating nucleocytoplasmic transport of at least some RNA. Here we show that efflux of two specific poly(A)-rich mRNAs (actin and beta-tubulin) from isolated L-cell nuclei is almost totally dependent on the presence of ATP, while efflux of poly(A)-free histone mRNA (H4, H2B, and H1) also occurs to a marked extent in the absence of this nucleotide. Measurements of temperature dependence of transport rate revealed an activation energy of 56.1 kJ/mol for actin mRNA, while the activation energy for histone-H4-mRNA efflux was in the same range as that found for ATP-induced release of RNA from demembranated nuclei (about 15-20 kJ/mol). Addition of nonhydrolyzable nucleotide analogs of ATP to the in vitro system used for measurement of RNA transport did not result in release of nonhistone mRNA (actin), but enhanced the efflux of H4 mRNA to approximately the same extent as ATP. Although not absolutely required, addition of ATP stimulated the rate of export of histone mRNA about twofold. Only the poly(A)-rich RNA, but not the poly(A)-free RNA, released from isolated nuclei was found to compete with poly(A) for the nuclear envelope mRNA-binding site, indicating the mechanism of transport for both RNA classes to be distinct. Export of both nonhistone and histone mRNA was found to be inhibited by a monoclonal antibody against a p60 nuclear-pore-complex antigen. This antibody had no effect on the nucleoside triphosphatase, mediating transport of poly(A)-rich mRNA.

Animals↗
PubMed1989

The La antigen shuttles between the nucleus and the cytoplasm in CV-1 cells.

Recently we established a monoclonal antibody against the La-protein (Bachmann et al., Proc. Natl. Acad. Sci. USA, 83, 7770, 1986). The antibody gives a nuclear speckled type staining and, in addition, a perinuclear cytoplasmic staining on cultured cells in immunofluorescence microscopy. After inhibition of RNA synthesis the La-protein is transported into the cytoplasm. After prolonged inhibition it returns into the nucleus forming large growing speckles. The transport into the nucleus apparently depends on glycosylation.

Animals↗
PubMed1989

Identification of La ribonucleoproteins as a component of interchromatin granules.

Monoclonal antibodies raised against the La antigen were used to localize by preembedding immunoelectron microscopy, snRNPs containing this protein. The results demonstrate that La RNPs are localized in clusters of interchromatin granules, both in Triton X-100-extracted and DNase-digested nuclei. DNase-digested salt-extracted nuclei contained, in addition, labeled structures identified as perichromatin granules and fibers. A close association of labeled granules with the nucleoli was also observed. Digestion of nuclei with DNase yielded residual scaffolds of intermediate filaments and nuclear lamina devoid of interchromatin granules and La immunostaining. Release of the La antigen was tested in the presence of ATP and cytochalasin B. Only cytochalasin was effective suggesting a role for nuclear actin in anchorage of snRNPs.

Antibodies, Monoclonal↗
PubMed1989

Change of processing and nucleocytoplasmic transport of mRNA in HSV-1-infected cells.

A monoclonal antibody (MAb) raised against the pore-complex lamina fraction from CV-1 cells was used to study alterations of gene expression in herpes simplex virus type 1 (HSV-1)-infected cells. This MAb, which recognized only one cellular polypeptide of 60,000 Da, selectively stained the nucleus in immunofluorescence microscopy, showing a punctuated pattern either at the nuclear surface or at the nuclear rim. By immunoelectron microscopy, the p60 antigen could be localized in the nuclear pore complex structure. Infection of CV-1 cells with HSV-1 resulted in a drastic change of the nuclear staining pattern. Four hours p.i., a clustering of the p60 antigen and, 12 h p.i., a formation of finger-like holes, penetrating the nucleus, occurred. Later in infection (22 h p.i.) the antigen was found to be almost absent. By RNA blot hybridization it was demonstrated that, after HSV-1 infection, the level of cellular mRNA (beta-tubulin) gradually decreased, while the level of HSV major DNA binding protein (DBP) mRNA increased, reaching maximal level 3-6 h p.i. Interestingly, the level of beta-tubulin gene transcripts changed differentially in the polysomal and in the nuclear fraction during the initial phase of infection, in contrast to the viral DBP transcripts, indicating that, after HSV infection, host cell transcripts accumulate in the nucleus. Evidence is presented indicating that this change is not due to altered nucleocytoplasmic mRNA transport but is due to an impaired splicing of host cell transcripts in HSV-infected cells. The MAb, directed against the nuclear pore p60 antigen, strongly inhibited the ATP-dependent efflux of both cellular and viral mRNA from isolated nuclei. The ATP-dependence of the efflux did not change during viral infection. However, the inhibitory potency of the MAb was found to be lost at the final stage of HSV infection, paralleling the loss of p60 antigen.

Adenosine Triphosphate↗
PubMed1989

Intracellular distribution of the La antigen in CV-1 cells after herpes simplex virus type 1 infection compared with the localization of U small nuclear ribonucleoprotein particles.

The La antigen is known to associate, at least transiently, with a series of small nuclear and cytoplasmic ribonucleoprotein particles (snRNPs and scRNPs), e.g. U1 and U6 snRNPs. In CV-1 cells a monoclonal antibody (MAb), directed against the La protein (La1B5), immunostained intranuclear speckles. These speckles were found to co-localize with speckles that were stained by MAbs directed against either all U snRNPs or only against U1 snRNPs. Two h after infection of CV-1 cells with herpes simplex virus type 1 (HSV-1) (strain HFEM) the staining of nuclear speckles with the anti-La MAb disappeared and the La protein was found quantitatively in the cytoplasm. In contrast nuclear speckles remained stained with the MAbs against the U snRNPs. Similar results were obtained using HSV-1 strains Lenette or 17 syn+ or temperature-sensitive (ts) mutants defective either in DNA synthesis (tsS) or in the immediate early protein (Mr 175 K) (tsK). Later in infection the La protein returned to the nucleus. Six h after infection most of the nuclear La protein was found to localize within patchy regions. These areas seem to be related to heterogeneous nuclear RNA transcription and/or processing sites, but not to DNA replication sites.

Antibodies, Monoclonal↗