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Biomedical subjects

M Ernst

Publications and source records attributed to M Ernst.

At least 127 records · Page 7Linked to original sources
PubMed1996

Human cytomegalovirus early infection, acute rejection, and major histocompatibility class II expression in transplanted lung. Molecular, immunocytochemical, and histopathologic investigations.

The present study aimed to investigate the relationship between acute rejection and human cytomegalovirus (HCMV) infection, as well as the coexpression of HLA-DR and immediate-early (IE) viral antigens, in 143 transbronchial biopsies and bronchoalveolar lavage fluids of 32 lung transplant recipients. We investigated the occurrence of morphologically overt viral infection with conventional histopathology, the expression of IE antigens with single labeling immunohistochemistry, the coexpression of IE antigens and HLA-DR molecules with double labeling techniques, and the presence of viral IE genes with polymerase chain reaction. Histopathologic study showed overt viral infections (12.6%) in 18 of the 143 biopsies; 8 were in a context of pneumonia and 10 were localizations without surrounding inflammatory cells; immunohistochemistry showed IE viral antigen expression in 31 (21.67%); PCR detected viral IE genes in 73/143 lavage fluids and biopsies (51%). The double labeling immunohistochemical technique showed that most IE antigen-expressing, noncytopathic cells were either HLA-DR negative in areas without infiltrates, or HLA-DR positive in those areas where inflammatory infiltrates were consistent, in the absence of viral cytopathy, with acute rejection. The results indicate that, in transplanted lung, the frequency of morphologically occult HCMV infection (as detected by immunohistochemically and/or PCR) is much higher than that of morphologically overt viral infection. The occurrence of inflammatory infiltrates (consistent with acute rejection) around morphologically occult infected cells and the possible lack of inflammation around both early- and late-infected cells suggest that in biopsies with occult infection the infiltrates should be attributed to allograft reaction. This conclusion would be in keeping with the coexpression of HLA-DR and HCMV IE in infiltrate-rich biopsies that are consistent with acute rejection, as well as with the absence of HLA-DR expression in IE antigen-positive cells in infiltrate-free-areas.

Acute Disease↗
PubMed1996

Fc gamma receptor I (CD64)-negative human monocytes are potent accessory cells in viral antigen-induced T cell activation and exhibit high IFN-alpha-producing capacity.

Blood monocytes represent a heterogeneous cell population with respect to phenotype and function. We have previously described that a minor subset of Fc gamma receptor I-negative (CD64-) monocytes, comprising < 10% of all monocytes, exhibits a significantly higher accessory capacity in allogeneic or purified protein derivative (PPD) of tuberculin-induced T cell activation than the majority of CD64-expressing (CD64+) monocytes. CD64- monocytes were also found to represent the major source of Newcastle disease virus (NDV)-induced interferon (IFN)-alpha within human monocytes. In the present study we demonstrate that CD64- monocytes are also the main producers of IFN-alpha in response to Herpes simplex virus type 1 (HSV-1) or influenza (type A) antigens. The virus-induced IFN-alpha release by monocytes, but mainly that by CD64- monocytes, can be further increased by co-culture with autologous T cells, which alone do not produce significant amounts of IFN-alpha in response to virus. In addition, CD64- and CD64+ monocytes also differ in their accessory capacity in virus-induced T cell responses. CD64- monocytes exposed to influenza antigens induced higher IFN-gamma release and proliferation by the responding autologous T cells than virus-exposed CD64+ monocytes. In virus-stimulated monocyte/T cell co-cultures, CD64- monocytes also induced larger size cell clusters than CD64+ monocytes, indicating direct cell-to-cell interaction with a higher number of T cells, which represent the main component of these clusters.

Antigen-Presenting Cells↗
PubMed1996

Solid-state NMR studies of the prion protein H1 fragment.

Conformational changes in the prion protein (PrP) seem to be responsible for prion diseases. We have used conformation-dependent chemical-shift measurements and rotational-resonance distance measurements to analyze the conformation of solid-state peptides lacking long-range order, corresponding to a region of PrP designated H1. This region is predicted to undergo a transformation of secondary structure in generating the infectious form of the protein. Solid-state NMR spectra of specifically 13C-enriched samples of H1, residues 109-122 (MKHMAGAAAAGAVV) of Syrian hamster PrP, have been acquired under cross-polarization and magic-angle spinning conditions. Samples lyophilized from 50% acetonitrile/50% water show chemical shifts characteristic of a beta-sheet conformation in the region corresponding to residues 112-121, whereas samples lyophilized from hexafluoroisopropanol display shifts indicative of alpha-helical secondary structure in the region corresponding to residues 113-117. Complete conversion to the helical conformation was not observed and conversion from alpha-helix back to beta-sheet, as inferred from the solid-state NMR spectra, occurred when samples were exposed to water. Rotational-resonance experiments were performed on seven doubly 13C-labeled H1 samples dried from water. Measured distances suggest that the peptide is in an extended, possibly beta-strand, conformation. These results are consistent with the experimental observation that PrP can exist in different conformational states and with structural predictions based on biological data and theoretical modeling that suggest that H1 may play a key role in the conformational transition involved in the development of prion diseases.

Amino Acid Sequence↗
PubMed1996

DNA polymorphisms in adhesion molecule genes--a new risk factor for early atherosclerosis.

To contribute to the analysis of the genetic background of atherosclerosis, especially endothelial dysfunction, we searched for DNA polymorphisms in the genes encoding E-, P-, and L-selectin, and ICAM-I and VCAM-I. We detected 17 mutations by single-strand conformation polymorphisms analysis and direct sequencing. Five of them resulted in an amino acid substitution. In E-selectin, exchanges from serine to arginine (position 128), from leucine to phenylalanine (position 554), and a DNA mutation from guanine to thymine (position 98) present significantly different allele frequencies in young patients with angiographically established, severe atherosclerosis, compared with an unselected population. Results suggest that these polymorphisms are associated with a higher risk for early severe atherosclerosis.

Adult↗
PubMed1996

Differential inhibition of neuronal and extraneuronal monoamine oxidase.

This study examined whether the neuronal and extraneuronal sites of action of two monoamine oxidase (MAO) inhibitors, l-deprenyl and debrisoquin, could be distinguished by their effects on plasma concentrations of catecholamine metabolites. Plasma concentrations of the intraneuronal deaminated metabolite of norepinephrine, dihydroxyphenylglycol (DHPG), were decreased by 77% after debrisoquin and by 64% after l-deprenyl administration. Plasma concentrations of the extraneuronal O-methylated metabolite of norepinephrine, normetanephrine, were increased substantially more during treatment with l-deprenyl than with debrisoquin (255% compared to a 27% increase). The comparable decreases in plasma concentrations of DHPG indicate a similar inhibition of intraneuronal MAO by both drugs. Much larger increases in normetanephrine after l-deprenyl than after debrisoquin are consistent with a site of action of the latter drug directed at the neuronal rather than the extraneuronal compartment. Thus, differential changes in deaminated and O-methylated amine metabolites allows identification of neuronal and extraneuronal sites of action of MAO inhibitors.

Adult↗
PubMed1996

Surgical therapy of gastrointestinal non-Hodgkin's lymphomas.

Within a period of 13 years 39 patients underwent surgery for primary gastrointestinal non-Hodgkin's lymphoma. The stomach was the most frequent site of involvement (26 cases) followed by the small intestine (10 cases) and the large bowel (three cases). Operative procedures included: total gastrectomy (n = 19), subtotal gastrectomy (n = 5), partial gastrectomy (n = 2), small bowel resection (n = 7), right hemicolectomy (n = 5) and sigmoid resection (n = 1). According to Musshoff's modification of the Ann Arbor system, we found stage I in nine, stage II in 12, stage III in two and stage IV in 16 patients. Histological typing according to the Kiel classification showed low-grade malignancy in 11 cases and high-grade in 28. Twenty-eight patients received chemotherapy and/or radiation in accordance with the tumour staging and type of malignancy. The follow-up data were analysed by the method of Kaplan and Meier. Including five patients who died post-operatively from perforated or bleeding lymphomas, the overall 5-year survival rate was 53.8%.

Adult↗
PubMed1996

Differential expression and function of CD80 (B7-1) and CD86 (B7-2) on human peripheral blood monocytes.

The interaction of CD28 with its ligands is important for T-cell activation. Recent studies demonstrated the existence of at least two ligands on accessory cells, CD80 (B7-1) and CD86 (B7-2). In this study we demonstrate that, although CD80 and CD86 are both expressed on monocytes, they seem to have different functions. Freshly isolated monocytes express CD86 but are CD80-negative. CD80 expression is weakly induced after 6-8 hr of in vitro culture and is enhanced by stimulation. CD86 expression is enhanced faster than CD80 expression and reaches the peak level after 4-6 hr in stimulated cells. Reverse transcription-polymerase chain reaction studies demonstrate that freshly isolated monocytes contain no CD80-mRNA. The mRNA of CD80 is induced after 4-6 hr of culture, which matches with the expression of the protein. Inhibition studies using different antibodies against both molecules and the fusion protein CTLA4Ig show that only anti-CD80 and CTLA4Ig could partially inhibit antigen-specific (tuberculin) and polyclonal (anti-CD3) lymphoproliferation and interferon-gamma (IFN-gamma) secretion of T cells cocultured with autologous monocytes. IFN-gamma secretion was more sensitive to blocking costimulation than proliferation. The antibody BB-1 did not inhibit proliferation and cytokine secretion, nor did the anti-CD86 clone IT2.2. CTLA4Ig, which binds both CD80 and CD86, has the same inhibitory capacity as the anti-CD80 antibody tested. From those findings we conclude that human monocytes use CD80 as a costimulatory ligand for CD28 and utilize other costimulatory mechanisms besides those mediated via molecules of the B7 family.

Antigens, CD↗
PubMed1996

The effect of cysteine modification and proteinases on the major antigens (D, C, c, E and e) of the Rh blood group system.

We have confirmed and extended previous observations showing that the (Rh) D antigen of erythrocyte membranes is destroyed by various reagents that modify cysteine (Cys) residues (Res.) and by trypsin as well as chymotrypsin, using thirty examples of monoclonal or polyclonal anti-D in heamglutination inhibition assays. We have also shown that most C, c, E, e and BS58 epitopes are inactivated or weakened by most Cys reagents and by these proteinases, using monoclonal and polyclonal antibodies. Inactivation by 5,5-dithiobis-(2-nitrobenzoic acid) was always fully reversible after subsequent dithioerythritol treatment. The essential Cys Res. appear to be buried in the membrane in view of the inability of some reagents to inactivate (iodoacetamide, iodoacetic acid) or reactivate (reduced glutathione) the antigens. Data obtained with N-ethylmaleimide indicate that inactivation of the C and c antigens is, at least in part, attributable to (a) Cys Res. that is (are) different from that (those) involved in the E and e antigens. Data obtained with the Cys reagents and the proteinases suggest that more than one peptide loop of the Rh proteins is involved in the major Rh antigens.

Cysteine↗
PubMed1996

Apoptosis of monocytes and prolonged survival of granulocytes as a result of phagocytosis of bacteria.

Monocytes and granulocytes were incubated with suspensions of Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, or Salmonella enteritidis and, after being washed free of bacteria, cultured for up to 48 h. Every few hours, samples of cultured cells were taken for DNA isolation. Monocytes which phagocytosed bacteria showed features of apoptotic cells, as determined by light microscopy and DNA fragmentation detected by gel electrophoresis. The phenomenon was observed 2 to 4 h after phagocytosis, in contrast, control monocytes did not show signs of apoptosis until 48 h of culture. Intact control granulocytes spontaneously became apoptotic after 12 h of culture. In contrast, degradation of DNA in cells exposed to bacteria was delayed by 12 to 24 h. In conclusion, our observation suggests that granulocytes and monocytes react differently to phagocytosis of bacteria.

Apoptosis↗
PubMed1996

Effect of in vitro infection of human monocytes with low numbers of Mycobacterium tuberculosis bacteria on monocyte apoptosis.

The effect of Mycobacterium tuberculosis H37Rv on spontaneous apoptosis of human monocytes from healthy donors in vitro was investigated. Infection with low numbers of viable M. tuberculosis bacteria prevented spontaneously occurring apoptosis in monocytes. Our data suggest that apoptosis of monocytes appears to be negatively associated with the presence of tumor necrosis factor alpha.

Apoptosis↗
PubMed1996

Selegiline in adults with attention deficit hyperactivity disorder: clinical efficacy and safety.

Clinical effects of high-dose and low-dose selegiline treatment were examined in 24 adults with attention deficit hyperactivity disorder (ADHD). The study used a double-blind randomized three-arm parallel-groups design with a 2-week placebo baseline followed by 6 weeks of treatment (placebo, 20 mg/day, or 60 mg/day selegiline) and then by 2 weeks of placebo post-treatment. A two-way repeated measures analysis of variance (ANOVA) showed no Drug x Time interaction and no main effect of Drug on severity of ADHD symptoms as self-rated by the subjects on the Conners Abbreviated Teacher Rating Scale (Conners ATRS). There was a significant effect of Time, indicating decreased ADHD symptom severity scores in all three groups. Selegiline treatment was not more effective than placebo. Side effects were more severe in the high-dose selegiline group than in either of the other groups. These preliminary results must be interpreted with caution because of methodological limitations in terms of sample size, patient population selection, and measurement tools.

Adult↗
PubMed1996

Cerebral glucose metabolism during pharmacologic studies: test-retest under placebo conditions.

UNLABELLED: The reliability of serial [18F]fluorodeoxyglucose (FDG) PET scans for psychopharmacologic studies was tested by using placebo infusions. METHODS: FDG scans were obtained before and after a 30 min placebo infusion (n = 10; Group 1) or after each of two bolus infusions with placebo (n = 8; Group 2). Subjects performed a continuous performance task (CPT) during each scan. Cardiovascular measures and ratings of anxiety were obtained in all subjects. Samples for determination of plasma norepinephrine (NE) were taken at multiple time points in Group 1. RESULTS: A slight increase in apparent global metabolism occurred between scans in both Groups 1 and 2. A few regions significantly increased in both groups. While an apparent increase in sympathetic activity occurred during the placebo infusion, neither NE levels, anxiety ratings nor cardiovascular measures correlated with global or regional FD6 uptake. CONCLUSION: Test-retest differences of global and regional glucose metabolism were highly consistent across two experimental designs. While increases in cerebral glucose metabolism appeared to occur during the second scan, differences between scans were small. This method may offer advantages for selected psychopharmacologic studies.

Adult↗
PubMed1995

The human germinal centre cells, follicular dendritic cells and germinal centre T cells produce B cell-stimulating cytokines.

Cytokine gene expression was investigated in the germinal centre constituents of follicular dendritic cells and germinal centre T cells and compared to the mRNA expression of nongerminal centre tonsillar cells. Cells were isolated from human tonsils by preenrichment with MACS and subsequent FACS sorting. Cytokine gene expression was investigated by intronspanning RT-PCR for IL-1 alpha, IL-1 beta, IL-2, IL-4, IL-5, IL-6, IL-10, IFN-alpha, IFN-beta, IFN-gamma, and TNF-alpha. Frequency of cytokine-producing cells and the cytokine production pattern of single cells were determined by single cell PCR. Furthermore, cytokine protein expression was investigated by immunohistology. Using these methods, we found a strong production of IL-1 beta mRNA and protein in a small percentage of FDC. Germinal centre T cells showed production of IL-2, IL-4, IL-10, IFN-gamma, and TNF-alpha mRNA. The mRNAs of these cytokines could also be detected at the single cell level; as they were produced in a high percentage of germinal centre T cells, whereas immunohistological staining was negative, we conclude that a high percentage of germinal centre T lymphocytes produce IL-2, IL-4, IL-10, IFN-gamma, and TNF-alpha in low concentrations in contrast to T cells outside the germinal centre, in which strong cytokine production in few cells was shown earlier.

B-Lymphocytes↗
PubMed1995

Follicular dendritic cells productively infected with immunodeficiency viruses transmit infection to T cells.

Lymphoid organs have been proposed to function as the major reservoir for the human immunodeficiency virus type 1 (HIV-1). Within lymphatic tissues germinal centers represent foci of rapidly proliferating B cells governed by the interaction between B and T cells and follicular dendritic cells (FDC). Accumulating evidence suggests an important role of FDC in the pathophysiology of the acquired immunodeficiency syndrome. Direct proof for the infectibility of FDC with HIV-1 has been lacking until recently when we were able to demonstrate a CD4-independent infection of FDC in vitro. Here we report that in vitro HIV-1-infected human FDC do not only contain proviral DNA, but also produce the virus, and transmit the infection to T cells. Furthermore, electron microscopical studies on ex vivo isolated FDC from simian immunodeficiency virus (SIV)-infected rhesus monkeys revealed typical virus budding. In addition, FDC from SIV-infected rhesus monkeys transmitted the infection to T cells in vitro. Due to this central role within the immune response FDC may serve as preferential targets for HIV both by trapping of virions on their surfaces and by productive infection. During disease FDC become productively infected and may, thus, be regarded as crucial elements in viral dissemination.

Animals↗
PubMed1995

The induction of bacillus-Calmette-Guérin-activated killer cells requires the presence of monocytes and T-helper type-1 cells.

Previously we have described the induction of MHC-unrestricted killer cells against bladder tumour cells by bacillus Calmette-Guérin (BCG), termed BCG-activated killer (BAK) cells. In the present paper we deal with the accessory-cell requirement for the activation of BAK cells. We show that monocytes are required for activating BAK cells, since no cytotoxicity can be induced in the absence of monocytes. Therefore, these phagocytes may represent the first step during the activation cascade of BAK cells. Furthermore, the presence of CD4+ T cells was essential for generating BAK cells: depleting peripheral blood mononuclear cells of CD4+ cells prior to stimulation with BCG abolished the cytotoxicity against bladder tumour cells. Experiments with monoclonal antibodies (mAb) neutralizing the activity of either interleukin-2 (IL-2) or interferon gamma (IFN gamma) underlined the importance of these cytokines: both mAb blocked the induction of BAK cells. Since both cytokines are related to the so-called Th1 pattern of T cells, we consider the second step of the generation of BAK cells as follows: monocytes presenting antigens of BCG trigger Th1-like cells in a preferred manner. These Th1-like T cells secrete IL-2 and IFN gamma and, thus, activate the BAK effector cells. Since CD4+ cells are dominant in the cells infiltrating the bladder wall after intravesical instillation of BCG in vivo, we postulate an important role for the Th1 subpopulation. We further postulate that the occurrence of macrophages in this infiltrate seems to be significant in the maintenance of the relapse-free state of the patient.

CD4-Positive T-Lymphocytes↗
PubMed1995

Elimination of monocytes from cultures activated with recall antigens.

Recent data provide evidence that antigen-specific CD4+ T-cell clones or antigen-activated T-cell lines can kill antigen-presenting cells (APC). We focused our studies on monocytes acting as APC in cultures of T cells freshly isolated from peripheral blood. The presence of monocytes in culture was monitored by their ability to emit light during phagocytosis of latex particles (latex-induced chemiluminescence). Using this approach as well as flow cytometry, evidence is presented that monocytes are eliminated from cultures with T cells activated with recall antigens (PPD or TT). The mechanism of monocyte elimination involved apoptosis as judged from in situ detection of DNA strand breaks by the terminal deoxynucleotidyl transferase assay. The antigen- but not lectin-dependent monocyte elimination was MHC-restricted and mediated by CD4+ T lymphocytes. This finding supports the hypothesis that elimination of APC is a general phenomenon during T-cell activation and may represent an important immunoregulatory mechanism.

Antigen-Presenting Cells↗