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Biomedical subjects

M Hagen

Publications and source records attributed to M Hagen.

At least 19 recordsLinked to original sources
PubMed2006

Mice deficient in galectin-1 exhibit attenuated physiological responses to chronic hypoxia-induced pulmonary hypertension.

Pulmonary hypertension (PH) is characterized by sustained vasoconstriction, with subsequent extracellular matrix (ECM) production and smooth muscle cell (SMC) proliferation. Changes in the ECM can modulate vasoreactivity and SMC contraction. Galectin-1 (Gal-1) is a hypoxia-inducible beta-galactoside-binding lectin produced by vascular, interstitial, epithelial, and immune cells. Gal-1 regulates SMC differentiation, proliferation, and apoptosis via interactions with the ECM, as well as immune system function, and, therefore, likely plays a role in the pathogenesis of PH. We investigated the effects of Gal-1 during hypoxic PH by quantifying 1) Gal-1 expression in response to hypoxia in vitro and in vivo and 2) the effect of Gal-1 gene deletion on the magnitude of the PH response to chronic hypoxia in vivo. By constructing and screening a subtractive library, we found that acute hypoxia increases expression of Gal-1 mRNA in isolated pulmonary mesenchymal cells. In wild-type (WT) mice, Gal-1 immunoreactivity increased after 6 wk of hypoxia. Increased expression of Gal-1 protein was confirmed by quantitative Western analysis. Gal-1 knockout (Gal-1(-/-)) mice showed a decreased PH response, as measured by right ventricular pressure and the ratio of right ventricular to left ventricular + septum wet weight compared with their WT counterparts. However, the number and degree of muscularized vessels increased similarly in WT and Gal-1(-/-) mice. In response to chronic hypoxia, the decrease in factor 8-positive microvessel density was similar in both groups. Vasoreactivity of WT and Gal-1(-/-) mice was tested in vivo and with use of isolated perfused lungs exposed to acute hypoxia. Acute hypoxia caused a significant increase in RV pressure in wild-type and Gal-1(-/-) mice; however, the response of the Gal-1(-/-) mice was greater. These results suggest that Gal-1 influences the contractile response to hypoxia and subsequent remodeling during hypoxia-induced PH, which influences disease progression.

Animals↗
PubMed2004

Asymptomatic cytomegalovirus infection is associated with increased risk of new-onset diabetes mellitus and impaired insulin release after renal transplantation.

AIMS/HYPOTHESIS: The human cytomegalovirus (CMV) may increase the risk of diabetes mellitus, but the literature is scarce. The present study was designed to test the hypothesis that asymptomatic CMV infection is associated with increased risk of new-onset diabetes after renal transplantation, and to assess the impact of asymptomatic CMV infection on OGTT-derived estimates of insulin release and insulin action. METHODS: A total of 160 consecutive non-diabetic renal transplant recipients on cyclosporine (Sandimmun Neoral)-based immunosuppression were closely monitored for CMV infection during the first 3 months after transplantation. All patients underwent a 75-g OGTT at 10 weeks. Excluded from the analyses were 36 patients with symptomatic CMV infection (disease). RESULTS: The incidence of new-onset diabetes was 6% in a control group of recipients without CMV infection (4/63) and 26% in the group with asymptomatic CMV infection (16/61). Asymptomatic CMV infection was associated with a significantly increased risk of new-onset diabetes (adjusted odds ratio: 4.00; 95% CI: 1.19 to 13.43, p=0.025). The group of patients with CMV infection had a significantly lower median insulin release than controls. CONCLUSIONS/INTERPRETATION: Our findings support the hypothesis that asymptomatic CMV infection is associated with increased risk of new-onset post-transplant diabetes mellitus, and suggest that impaired insulin release may involve one pathogenetic mechanism.

Antigens, Viral↗
PubMed1999

Self-splicing of the Tetrahymena intron from mRNA in mammalian cells.

The Tetrahymena pre-rRNA self-splicing intron is shown to function in the unnatural context of an mRNA transcribed by RNA polymerase II in mammalian cells. Mutational analysis supports the conclusion that splicing in cells occurs by the same RNA-catalyzed mechanism established for splicing in vitro. Insertion of the intron at five positions spanning the luciferase open reading frame revealed 10-fold differences in accumulation of ligated exons and in luciferase activity; thus, the intron self-splices in many exon contexts, but the context can have a significant effect on activity. In addition, even the best self-splicing constructs, which produced half as much mRNA as did an uninterrupted luciferase gene, gave approximately 100-fold less luciferase enzyme activity, revealing an unexpected discontinuity between mRNA production and translation in cells. The finding that production of accurately spliced mRNA in cells does not guarantee a corresponding level of protein production is surprising, and may have implications for the development of trans-splicing ribozymes as therapeutics.

Amino Acid Substitution↗
PubMed1999

A regulatory role for Fc gamma receptors (CD16 and CD32) in hematopoiesis.

Progenitor cells of the T- and B-lineages in mice express (CD32) and Fc gamma RIII (CD16) but as the developing lymphocytes begin to express clonal antigen receptors, CD16 and CD32 are downregulated in T-cells, and CD16 is downregulated in B-cells. Considering that counter-receptors for Fc gamma R occur on thymic and bone marrow stromal cells, the possibility exists that Fc gamma R might participate in some aspect of T- and B-lineage development prior to the stage of antigen receptor expression. Previous studies provided evidence that Fc gamma R can influence murine T-lineage development. In the present studies we found that anti-Fc gamma RII/III mAb accelerated B-lineage development in bone marrow cultures from normal mice, but not in cultures from CD16-/- or CD32-/- mice. Similar results were observed when FACS-purified B-progenitor cells were co-cultured with BMS2, a bone marrow stromal cell line. Fresh bone marrow from CD32-/- mice contained about two-fold more B-lineage cells compared to bone marrow from normal or CD16-/- mice. These studies indicate that the Fc gamma R on B-lineage progenitor cells can influence their further development and add to a growing body of evidence that implicates Fc gamma R as regulatory elements in hematopoiesis.

Animals↗
PubMed1998

Atypical pulmonary eosinophilia is mediated by a specific amino acid sequence of the attachment (G) protein of respiratory syncytial virus.

We analyzed the immune responses evoked by a series of overlapping peptides to better understand the molecular basis for respiratory syncytial virus (RSV) G protein-induced eosinophilia in BALB/c mice. In vitro stimulation of spleen cells from natural G protein-primed mice showed dominant proliferative and cytokine (interferon [IFN]-gamma and interleukin [IL]-5) responses to a peptide encompassing amino acids 184-198. Mice vaccinated with peptide 184- 198 conjugated to keyhole limpet hemocyanin showed significant pulmonary eosinophilia (39.5%) after challenge with live RSV. In contrast, mice immunized with a peptide (208-222) conjugate associated with induction of IFN-gamma secreting spleen cells did not exhibit pulmonary eosinophilia after challenge. The in vivo depletion of CD4(+) cells abrogated pulmonary eosinophilia in mice vaccinated with the peptide 184-198 conjugate, whereas the depletion of CD8(+) cells had a negligible effect. Therefore, we have identified an association between peptide 184- 198 of natural G protein and the CD4(+) T cell-mediated induction of pulmonary eosinophilia after live RSV challenge. Out of 43 human donors, 6 provided peripheral blood mononuclear cells that showed reactivity to G protein from RSV A2, 3 of which responded to peptide 184- 198. The results have important implications for the development of a vaccine against RSV.

Amino Acid Sequence↗
PubMed1998

Sulfotransferase-mediated activation of mutagens studied using heterologous expression systems.

Sulfation is a common final step in the biotransformation of xenobiotics and is traditionally associated with inactivation. However, the sulfate group is electron-withdrawing and may be cleaved off heterolytically in some molecules leading to electrophilic cations which may form adducts with DNA and other important cellular structures. Since endogenous sulfotransferases do not appear to be expressed in indicator cells of standard mutagenicity tests, rat and human sulfotransferases have been stably expressed in his- Salmonella typhimurium strain TA1538 and Chinese hamster V79 cells. Using these recombinant indicator cells, sulfotransferase-dependent genotoxic activities were detected with N-hydroxy-2-acetylaminofluorene, 2-acetylaminofluorene (in the presence of co-expressed rat cytochrome P450 1A2), hycanthone, 1'-hydroxysafrole, alpha-hydroxytamoxifen and various benzylic alcohols derived from polycyclic aromatic hydrocarbons. In several cases, it was critical that the reactive sulfuric acid conjugates were formed directly within the indicator cells, owing to the inefficient penetration of cell membranes. In other cases, spontaneous benzylic substitution reactions with medium components, such as halogenide ions or amino acids, led to secondary, membrane-penetrating reactive species. Different sulfotransferases, including related forms from rat and human, substantially differed in their substrate specificity towards the investigated promutagens. It is known that some sulfotransferases are expressed with high tissue and cell type specificities. This site-dependent expression together with the limitations in the distribution of reactive sulfuric acid conjugates may explain organotropic effects of compounds activated by this metabolic pathway.

Animals↗
PubMed1998

Expression of human estrogen sulfotransferase in Salmonella typhimurium: differences between hHST and hEST in the enantioselective activation of 1-hydroxyethylpyrene to a mutagen.

Various human sulfotransferases (hP-PST, hM-PST, hHST) and rat sulfotransferases (rPST-IV, rHSTa) have already been expressed in Ames' Salmonella strains (in particular in TA1538). Now a further strain, TA1538-hEST, which expresses the human estrogen sulfotransferase (hEST), has been constructed. This strain activated the primary benzylic alcohol 1-hydroxymethylpyrene (1-HMP) and the secondary benzylic alcohol 1-hydroxyethylpyrene (1-HEP) to mutagens. Human sulfotransferases hEST and hHST both activated 1-HEP, but they differed substantially in their enantioselectivity for this compound.

Animals↗
PubMed1998

Characterization of thyroid hormone sulfotransferases.

Sulfation is an intriguing pathway of thyroid hormone metabolism since it facilitates the degradation of the hormone by the type I deiodinase (D1). This study reports the preliminary characterization of iodothyronine sulfotransferase activities of rat and human liver cytosol and recombinant rSULT1C1 and hSULT1A1 isoenzymes. All these enzyme preparations catalyzed the sulfation of--in decreasing order of efficiency--3,3'-diiodothyronine (3,3'-T2) > 3,3',5-triiodothyronine (T3) approximately 3,3',5'-triiodothyronine (rT3) > thyroxine (T4). 3,3'-T2 sulfotransferase activity was found to be higher in male than in female rat liver, which has also been shown by others for the expression of rSULT1A1 and rSULT1C1. No sulfation of iodothyronines was observed with rSULT1A1. Different phenol derivatives were found to be potent inhibitors of the sulfation of 3,3'-T2 by native and recombinant sulfotransferases, with pentachlorophenol and 2,4,6-tribromophenol being the most potent. The inhibitions exerted by the different phenols on 3,3'-T2 sulfation by rSULT1C1 correlated better with the effects observed in male than with those in female liver. A strong correlation was also observed between the inhibition profiles of human liver cytosol and hSUL1T1A1. These results suggest that: (1) rSULT1C1 is an important isoenzyme for the sulfation of thyroid hormone in male rat liver; (2) another isoenzyme with similar properties, perhaps rSULT1B1, is responsible for thyroid hormone sulfation in female rat liver and may also contribute to this process in male rat liver; and (3) hSULT1A1 is an important isoenzyme for thyroid hormone sulfation in human liver.

Animals↗
PubMed1998

Survival after in-hospital cardiopulmonary resuscitation. A meta-analysis.

OBJECTIVE: To determine the rates of immediate survival and survival to discharge for adult patients undergoing in-hospital cardiopulmonary resuscitation, and to identify demographic and clinical variables associated with these outcomes. MEASUREMENTS AND MAIN RESULTS: The MEDLARS database of the National Library of Medicine was searched. In addition, the authors' extensive personal files and the bibliography of each identified study were searched for further studies. Two sets of inclusion criteria were used, minimal (any study of adults undergoing in-hospital cardiopulmonary resuscitation) and strict (included only patients from general ward and intensive care units, and adequately defined cardiopulmonary arrest and resuscitation). Each study was independently reviewed and abstracted in a nonblinded fashion by two reviewers. The data abstracted were compared, and any discrepancies were resolved by consensus discussion. For the subset of studies meeting the strict criteria, the overall rate of immediate survival was 40.7% and the rate of survival to discharge was 13.4%. The following variables were associated with failure to survive to discharge: sepsis on the day prior to resuscitation (odds ratio [OR] 31.3; 95% confidence interval [CI] 1.9, 515), metastatic cancer (OR 3.9; 95% CI 1.2, 12. 6), dementia (OR 3.1; 95% CI 1.1, 8.8), African-American race (OR 2. 8; 95% CI 1.4, 5.6), serum creatinine level at a cutpoint of 1.5 mg/dL (OR 2.2; 95% CI 1.2, 3.8), cancer (OR 1.9; 95% CI 1.2, 3.0), coronary artery disease (OR 0.55; 95% CI 0.4, 0.8), and location of resuscitation in the intensive care unit (OR 0.51; 95% CI 0.4, 0.8). CONCLUSIONS: When talking with patients, physicians can describe the overall likelihood of surviving discharge as 1 in 8 for patients who undergo cardiopulmonary resuscitation and 1 in 3 for patients who survive cardiopulmonary resuscitation.

Adult↗
PubMed1998

Homing of transgenic gammadelta T cells into murine vaginal epithelium.

The vaginal epithelium of normal mice contains lymphocytes of fetal thymic origin that express an invariant Vgamma4/Vdelta1 TCR. The apparent lack of other gammadelta TCR species suggests that a selection mechanism might operate to regulate the localization of gammadelta T cells at this anatomical site. Selection might be connected to the Vgamma4/Vdelta1 TCR or to some homing characteristic of the fetal thymic lineage that appears at day 17-18 of embryonic life. In the present studies, we investigated whether transgenic gammadelta cells expressing a TCR species characteristic of the subpopulation of gammadelta T cells found in the blood, spleen and lymph would translocate to the vaginal epithelium. We found that the transgenic Vgamma2 TCR+ cells did accumulate in the vagina of transgenic mice. Furthermore, like normal vaginal gammadelta T cells, the transgenic vaginal gammadelta T cells expressed the phenotype of recently activated memory/effector T cells (CD44(hi), CD62L-, CD45RB(lo), CD69+). Vaginal gammadelta T cells in normal mice do not express the CD2 and CD28 antigens, but both of these markers are present on transgenic vaginal gammadelta T cells. We observed that a small fraction of splenic transgenic gammadelta T cells had the same surface phenotype as the vaginal transgenic gammadelta T cells, raising the possibility that the gammadelta T cells present in the vaginal epithelium of transgenic mice originated from the peripheral lymphoid organs. Data in support of this possibility came from experiments in which co-incubation of splenic transgenic gammadelta T cells with vaginal epithelial cell suspensions induced the vaginal gammadelta phenotype on the splenic gammadelta T cells. The finding of transgenic gammadelta T cells in the vaginal epithelium suggests that homing of gammadelta T cells to this site is not restricted to gammadelta T cells that express the V4/NS1 invariant TCR. Furthermore, these findings imply that retention of gammadelta T cells in the vaginal epithelium of normal mice is affected by a Vgamma4/Vdelta1-specific mechanism. The finding of a significant level of apoptosis in the transgenic vaginal gammadelta T cells, but not in the normal vaginal gammadelta T cells, could reflect that the mechanism of retention of Vgamma4/Vdelta1 + in the vaginal epithelium involves selective survival at the site.

Animals↗
PubMed1997

The effect of structure in a long target RNA on ribozyme cleavage efficiency.

Inhibition of gene expression by catalytic RNA (ribozymes) requires that ribozymes efficiently cleave specific sites within large target RNAs. However, the cleavage of long target RNAs by ribozymes is much less efficient than cleavage of short oligonucleotide substrates because of higher order structure in the long target RNA. To further study the effects of long target RNA structure on ribozyme cleavage efficiency, we determined the accessibility of seven hammerhead ribozyme cleavage sites in a target RNA that contained human immunodeficiency virus type 1 (HIV-1) vif - vpr . The base pairing-availability of individual nucleotides at each cleavage site was then assessed by chemical modification mapping. The ability of hammerhead ribozymes to cleave the long target RNA was most strongly correlated with the availability of nucleotides near the cleavage site for base pairing with the ribozyme. Moreover, the accessibility of the seven hammerhead ribozyme cleavage sites in the long target RNA varied by up to 400-fold but was directly determined by the availability of cleavage sites for base pairing with the ribozyme. It is therefore unlikely that steric interference affected hammerhead ribozyme cleavage. Chemical modification mapping of cleavage site structure may therefore provide a means to identify efficient hammerhead ribozyme cleavage sites in long target RNAs.

Base Composition↗
PubMed1997

Lack of Fc-epsilon receptors on murine eosinophils: implications for the functional significance of elevated IgE and eosinophils in parasitic infections.

Chronic infection with Schistosoma mansoni induces in humans and mice a Th2-dominant immune response in which eosinophils and IgE are conspicuously elevated. Human eosinophils express IgE receptors that participate in an IgE-dependent eosinophil-mediated ADCC reaction against Schistosomula larvae in vitro. To investigate the expression of IgE receptors on murine eosinophils, they were purified (>95% pure by Giemsa-stained cytospin preparations) from liver granulomas of Schistosoma-infected mice. Flow cytometric analysis showed the absence of the low-affinity IgE receptor Fc-epsilon RII (CD23) and Mac-2 and the absence of binding of murine IgE. Reverse transcription-polymerase chain reaction (RT-PCR) analysis of granuloma eosinophil mRNA did not detect transcripts for Fc-epsilon RII or the alpha-chain of the high-affinity IgE receptor Fc-epsilon RI, but did detect transcripts that encode Mac-2 and the low-affinity IgG receptors Fc-gamma RIIb2, Fc-gamma RIII, and the FcR-associated gamma-chain. In vitro stimulation of granuloma eosinophils with interleukin-4 (IL-4) did not induce IgE binding, surface expression of Mac-2, or the transcription of Fc-epsilon receptors (Fc-epsilon RI, Fc-epsilon RII/CD23). To investigate normal murine eosinophils, we cultured normal mouse bone marrow cells with recombinant IL-3, recombinant IL-5, and recombinant granulocyte-macrophage colony-stimulating factor, conditions that promote eosinophil differentiation. Flow cytometric analysis of bone marrow-derived eosinophils failed to detect IgE binding or cell surface expression of Fc-epsilon RII and Mac-2, and RT-PCR analysis of fluorescence-activated cell sorted bone marrow-derived eosinophils failed to detect transcripts that encode Fc-epsilon RI or Fc-epsilon RII. These findings show that, in contrast to human eosinophils, murine eosinophils do not express cell surface receptors that bind IgE. However, because IgG receptors (Fc-gamma RIIb2, Fc-gamma RII) were present on eosinophils purified from granulomas, we investigated whether they might be involved in eosinophil activation. We found that an oxidative burst in eosinophils could be triggered through their IgG receptors.

Animals↗
PubMed1997

Gamma delta T cells of the murine vagina: T cell response in vivo in the absence of the expression of CD2 and CD28 molecules.

While little is known about their activation requirements and function, the intraepithelial T cells of the murine vagina express TCR complexes in which the antigen recognition components and the signaling components have unusual features. These vaginal T cells express an invariant V gamma 4/V delta 1 TCR and appear to be the only intraepithelial gamma delta T cells that exclusively use FcR gamma chains in their TCR complex. To further characterize the vaginal gamma delta T cells we isolated them from normal mice and from mice injected systemically with an activation-inducing dose of anti-TCR mAb. The isolated gamma delta T cells were examined by flow cytometry for their surface expression of a panel of adhesion, proteins, activation antigens and cellular interaction molecules (CD44, CD62L, CD45RB, LFA-1, CD2 and CD28). The patterns of expression observed indicate that the vaginal gamma delta T cells of normal mice show the phenotype of effector T cells. The adhesion/co-stimulatory molecules CD28 and CD2 were not detected on vaginal gamma delta T cells, an interesting finding since the absence of CD2 from other T cells has been suggested to result in anergy. However, vaginal gamma delta T cells are responsive to TCR-mediated signals since injection of normal mice with pan-anti-TCR antibody or stimulating anti-gamma delta TCR antibody resulted in an increase in cell number and increased expression of transferrin and IL-2 receptors. These results indicate that vaginal gamma delta T cells might utilize other co-stimulatory molecules, if any, in connection with TCR-induced activation and differentiation. While the physiological function of vaginal gamma delta T cells remains unknown, the expression of an invariant V gamma 4/V delta 1 TCR, their exclusive use of gamma chain homodimers in their TCR, and the absence of CD2 and CD28 co-stimulatory molecules are a novel combination of properties that suggests specialized functional properties. Although vaginal gamma delta T cells share some features in common with gamma delta T cells that reside in other epithelial tissues, such as skin and intestine, the present studies provide additional evidence that vaginal gamma delta T cells are a highly specialized and distinct T cell population.

Animals↗
PubMed1996

Activation features of intraepithelial gamma delta T-cells of the murine vagina.

The epithelium of the murine vagina contains a resident population of gamma delta T-cells that expresses a homogenous Vgamma4/Vdelta1 TCR lacking N-region junctional diversity, implying that these T-cells recognize a very limited array of antigenic structures. The vaginal gamma delta T-cells express a pattern of surface markers characteristic of memory/effector T-cells that have previously been activated. Although vaginal gamma delta T-cells do not express the major costimulatory molecules CD28 and CD2, they do proliferate in response to a systemically delivered anti gamma delta TCR stimulus. Vaginal gamma delta T-cells contain mRNA that encodes the keratinocyte growth factor raising the possibility that these cells play a role in the repair of vaginal epithelium following injury. While the antigen recognized by the vaginal gamma delta TCR is unknown, a model is proposed which attempts to relate some of the unusual phenotypic features of vaginal gamma delta T-cells to the physiological injury and shedding of vaginal epithelium that occurs during the estrous cycle.

Animals↗
PubMed1995

Human platelet phenolsulfotransferases: cDNA cloning, stable expression in V79 cells and identification of a novel allelic variant of the phenol-sulfating form.

We have isolated cDNA clones encoding phenol- and monoamine-sulfating phenolsulfotransferases, using the reverse transcription-polymerase chain reaction method with human platelet mRNA as template. These cDNAs were stably expressed in the Chinese hamster fibroblast cell line V79 and their substrate specificities towards known sulfotransferase isoenzyme-selective compounds determined. The nucleotide and derived amino acid sequences of the monoamine-sulfating form were identical to those previously identified in human liver and brain, but the cDNA for the human platelet phenol-sulfating form we isolated contained 5 and 2 amino acid changes from the two previously published sequences from human liver and brain, suggesting that we have identified a new allelic variant of human phenol-sulfating phenolsulfotransferase.

Alleles↗